Chapter 15. Input Devices

Keyboards

One of the most basic system components is the keyboard, which is the primary input device. Keyboards are used for entering commands and data into the system. This section looks at keyboards for PCs, examining the various types of keyboards, how they function, the keyboard-to-system interfaces, and keyboard troubleshooting and repair.

In the years following the introduction of the original IBM PC, IBM created three keyboard designs for PC systems, and since then Microsoft has augmented one of them. Together these designs have become de facto standards in the industry and are shared by virtually all PC manufacturers.

The primary keyboard types are as follows:

• 101-key Enhanced keyboard

• 104-key Windows keyboard

• 83-key PC and XT keyboard (obsolete)

• 84-key AT keyboard (obsolete)

This section discusses the 101-key Enhanced and 104-key Windows keyboards, showing the layout and physical appearance of both. Although you may still find old 83-key and 84-key designs, these are rare today.

Enhanced 101-Key Keyboard

In 1986, IBM introduced the Enhanced 101-key keyboard for the XT and AT models. This design first appeared in IBM’s RT PC, which was a RISC (reduced instruction set computer) system designed for scientific and engineering applications. Keyboards with this design were soon supplied with virtually every type of system and terminal IBM sold. Other companies quickly copied this design, which became the standard on virtually all PCs until the introduction of the 104-key Windows keyboard in 1995 (discussed later in this chapter).

The layout of the enhanced keyboard was improved over that of the 84-key unit, with the possible exception of the Enter key, which reverted to a smaller size. The 101-key Enhanced keyboard was designed to conform to international regulations and specifications for keyboards. In fact, other companies such as Digital Equipment Corporation (DEC) and Texas Instruments (TI) had already been using designs similar to the IBM 101-key unit. The IBM 101-key units originally came in versions with and without the status-indicator LEDs, depending on whether the unit was sold with an XT or AT system. (XT systems didn’t support the LEDs.) Currently there are many variations from which to choose, including some with integrated pointing devices, such as the IBM TrackPoint pointing stick, trackballs, and/or touch pads, as well as programmable keys useful for automating routine tasks.

IBM (with its Lexmark keyboard and printer spin-off) and Unicomp (which now produces these keyboards) have produced a number of keyboard models, including versions with built-in pointing devices and new ergonomic layouts. Several connector variations are possible as well. Whereas PC keyboards started out using a larger 5-pin DIN (an acronym for Deutsches Institut für Normung e.V.) keyboard connector, current designs use either the smaller 6-pin mini-DIN connector (often called a PS/2 connector because it first came on the IBM PS/2 systems) or industry standard USB.

Although the connectors might be physically different between the larger and smaller DIN types, the keyboards are not, and you can either interchange the cables or use a cable adapter to plug one type in to the other; some keyboards you can buy at retail include the adapter in the package. See the section “Keyboard/Mouse Interface Connectors” and Figure 15.8, later in this chapter, for the physical and electronic details of these connectors. Many keyboards now include both the standard mini-DIN as well as USB connectors for maximum flexibility when attaching to newer systems. See the section “USB Keyboards,” later in this chapter, for details on connecting keyboards via USB.

The 101-key keyboard layout can be divided into the following four sections:

• Typing area

• Numeric keypad

• Cursor and screen controls

• Function keys

The 101-key arrangement is similar to the Selectric keyboard layout, with the exception of the Enter key. The Tab, Caps Lock, Shift, and Backspace keys have a larger striking area and are located in the familiar Selectric locations. The Ctrl and Alt keys are on each side of the spacebar, and the typing area and numeric keypad have home-row identifiers for touch typing.

The cursor- and screen-control keys have been separated from the numeric keypad, which is reserved for numeric input. (As with other PC keyboards, you can use the numeric keypad for cursor and screen control when the keyboard is not in Num Lock mode.) A division-sign key (/) and an additional Enter key have been added to the numeric keypad.

The cursor-control keys are arranged in the inverted T format that is now expected on all computer keyboards. The Insert, Delete, Home, End, Page Up, and Page Down keys, located above the dedicated cursor-control keys, are separate from the numeric keypad. The function keys, spaced in groups of four, are located across the top of the keyboard. The keyboard also has two additional function keys: F11 and F12. The Esc key is isolated in the upper-left corner of the keyboard. In addition, dedicated Print Screen/Sys Req, Scroll Lock, and Pause/Break keys are provided for commonly used functions.

Foreign-language versions of the Enhanced keyboard include 102 keys and a slightly different layout from the 101-key U.S. versions.

One of the many useful features of the IBM/Lexmark enhanced keyboard (now manufactured by Unicomp) is removable keycaps. This permits the replacement of broken keys and provides access for easier cleaning. Also, with clear keycaps and paper inserts, you can customize the keyboard. Keyboard templates are also available to provide specific operator instructions.

104-Key (Windows) Keyboard

When Microsoft released Windows 95, it also introduced the Microsoft Natural Keyboard, which implemented a revised keyboard specification that added three new Windows-specific keys to the keyboard.

The Microsoft Windows keyboard specification, which has since become standard for many desktop and laptop keyboards, outlines a set of additional keys and key combinations. The 104-key layout includes left and right Windows keys and an Application key (see Figure 15.1). These keys are used for operating system and application-level keyboard combinations, similar to the existing Ctrl and Alt combinations. You don’t need these keys to use Windows, but many software vendors have added specific functions to their Windows products that use the Application key (which provides the same functionality as clicking the right mouse button). The recommended Windows keyboard layout calls for the left and right Windows keys (called WIN keys) to flank the Alt keys on each side of the spacebar, as well as an Application key on the right of the right Windows key. Note that the exact placement of these keys is up to the keyboard designer, so variations exist from keyboard to keyboard.

Figure 15.1 The 104-key Windows keyboard layout.

The WIN keys open the Windows Start menu, which you can then navigate with the cursor keys. The Application key simulates the right mouse button; in most applications, it brings up a context-sensitive pop-up menu. Several WIN key combinations offer preset macro commands as well. For example, you can press WIN+E to launch the Windows Explorer application. Table 15.1 shows a list of common Windows key combinations used with the 104-key keyboard.

Table 15.1 Windows Key Combinations

The Windows and Application keys are not mandatory when running Windows. In fact, preexisting standard key combinations can perform the same functions as these newer keys.

The Windows keyboard specification requires that keyboard makers increase the number of trilograms in their keyboard designs. A trilogram is a combination of three rapidly pressed keys that perform a special function, such as Ctrl+Alt+Delete. Designing a keyboard so that the switch matrix correctly registers the additional trilograms plus the additional Windows keys adds somewhat to the cost of these keyboards compared to the previous 101-key standard models.

Many keyboard manufacturers have standardized on 104-key keyboards that include these Windows-specific keys. Some manufacturers have added browser control or other keys that, although not standard, can make them easier to use for navigating web pages and launching various applications.

Foreign-language versions of the Windows keyboard include 105 keys and a slightly different layout from the 104-key U.S. versions.

For additional keyboard combinations you can use, see “Running Windows Without a Mouse” in the Technical Reference section of the disc included with this book.

Keyboard Technology

The technology that makes up a typical PC keyboard is very interesting. This section focuses on all the aspects of keyboard technology and design, including the keyswitches, the interface between the keyboard and the system, the scan codes, and the keyboard connectors.

Keyswitch Design

Today’s keyboards use any one of several switch types to create the action for each key. Most keyboards use a variation of the mechanical keyswitch. A mechanical keyswitch relies on a mechanical momentary contact-type switch to make the electrical contact that forms a circuit. Some high-end keyboards use a more sophisticated design that relies on capacitive switches. This section discusses these switches and the highlights of each design.

The most common type of keyswitch is the mechanical type, available in the following variations:

• Pure mechanical

• Foam element

• Rubber dome

• Membrane

Pure Mechanical Switches

The pure mechanical type is just that—a simple mechanical switch that features metal contacts in a momentary contact arrangement. The switch often includes a tactile feedback mechanism, consisting of a clip and spring arrangement designed to give a “clicky” feel to the keyboard and offer some resistance to the keypress (see Figure 15.2).

Figure 15.2 A typical mechanical switch used in older NMB Technologies keyboards. As the key is pressed, the switch pushes down on the contacts to make the connection.

Mechanical switches are very durable, usually have self-cleaning contacts, and are normally rated for 20 million keystrokes (which is second only to the capacitive switch in longevity). They also offer excellent tactile feedback.

Despite the tactile feedback and durability provided by mechanical keyswitch keyboards, they have become much less popular than membrane keyboards (discussed later in this chapter). In addition, many companies that produce keyboards that use mechanical keyswitches either use them for only a few of their high-priced models or have phased out their mechanical keyswitch models entirely. With the price of keyboards nose-diving along with other traditional devices, such as mice and drives, the pressure on keyboard makers to cut costs has led many of them to abandon or deemphasize mechanical-keyswitch designs in favor of the less expensive membrane keyswitch.

The Alps Electric mechanical keyswitch is used by many of the vendors who produce mechanical-switch keyboards, including Alps Electric itself. Other vendors who use mechanical keyswitches for some of their keyboard models include Adesso, Inc. (www.adesso.com), Avant Prime and Stellar (revivals of the classic Northgate keyboards are available from Ergonomic Resources; www.ergonomicsmadeeasy.com), Kinesis (www.kinesis-ergo.com), and SIIG (www.siig.com). Many of these vendors sell through the OEM market, so you must look carefully at the detailed specifications for the keyboard to see whether it is a mechanical keyswitch model.

Foam Element Switches

Foam element mechanical switches were a very popular design in some older keyboards. Most of the older PC keyboards, including models made by Key Tronic and many others, used this technology. These switches are characterized by a foam element with an electrical contact on the bottom. This foam element is mounted on the bottom of a plunger that is attached to the key (see Figure 15.3).

Figure 15.3 Typical foam element mechanical keyswitch.

When the switch is pressed, a foil conductor on the bottom of the foam element closes a circuit on the printed circuit board below. A return spring pushes the key back up when the pressure is released. The foam dampens the contact, helping to prevent bounce, but unfortunately it gives these keyboards a “mushy” feel. The big problem with this type of keyswitch design is that little tactile feedback often exists. These types of keyboards send a clicking sound to the system speaker to signify that contact has been made. Preferences in keyboard feel are somewhat subjective; I personally do not favor the foam element switch design.

Another problem with this type of design is that it is more subject to corrosion on the foil conductor and the circuit board traces below. When this happens, the key strikes can become intermittent, which can be frustrating. Fortunately, these keyboards are among the easiest to clean. By disassembling the keyboard completely, you usually can remove the circuit board portion—without removing each foam pad separately—and expose the bottoms of all the pads. Then, you easily can wipe the corrosion and dirt off the bottoms of the foam pads and the circuit board, thus restoring the keyboard to a “like-new” condition. Unfortunately, over time, the corrosion problem will occur again. I recommend using some Stabilant 22a from D.W. Electrochemicals (www.stabilant.com) to improve the switch contact action and prevent future corrosion. Because of such problems, the foam element design is not used much anymore and has been superseded in popularity by the rubber dome design.

KeyTronicEMS, the most well-known user of this technology, now uses a center-bearing membrane switch technology in its keyboards, so you are likely to encounter foam-switch keyboards only on very old systems.

Rubber Dome Switches

Rubber dome switches are mechanical switches similar to the foam element type but are improved in many ways. Instead of a spring, these switches use a rubber dome that has a carbon button contact on the underside. As you press a key, the key plunger presses on the rubber dome, causing it to resist and then collapse all at once, much like the top of an oil can. As the rubber dome collapses, the user feels the tactile feedback, and the carbon button makes contact between the circuit board traces below. When the key is released, the rubber dome re-forms and pushes the key back up.

The rubber eliminates the need for a spring and provides a reasonable amount of tactile feedback without any special clips or other parts. Rubber dome switches use a carbon button because it resists corrosion and has a self-cleaning action on the metal contacts below. The rubber domes themselves are formed into a sheet that completely protects the contacts below from dirt, dust, and even minor spills. This type of switch design is the simplest, and it uses the fewest parts. This made the rubber dome keyswitch very reliable for several years. However, its relatively poor tactile feedback has led most keyboard manufacturers to switch to the membrane switch design covered in the next section.

Membrane Switches

The membrane keyswitch is a variation on the rubber dome type, using a flat, flexible circuit board to receive input and transmit it to the keyboard microcontroller. Industrial versions of membrane boards use a single sheet for keys that sits on the rubber dome sheet for protection against harsh environments. This arrangement severely limits key travel. For this reason, flat-surface membrane keyboards are not considered usable for normal touch typing. However, they are ideal for use in extremely harsh environments. Because the sheets can be bonded together and sealed from the elements, membrane keyboards can be used in situations in which no other type could survive. Many industrial applications use membrane keyboards for terminals that do not require extensive data entry but are used instead to operate equipment, such as cash registers and point-of-sale terminals in restaurants.

Membrane keyswitches are not just relegated to fast food or industrial uses, though. The membrane keyswitch used with conventional keyboard keytops has become the most popular keyswitch used in low-cost to mid-range keyboards, and even some high-end units. Although low-end membrane keyswitches have a limited life of only 5–10 million keystrokes, some of the better models are rated to handle up to 20 million keystrokes, putting them in the range of pure mechanical switches for durability (see Figure 15.4). A few membrane switches are even more durable: Cherry Corporation’s G8x-series keyboards use Cherry’s own 50-million-keystroke membrane switch design (www.cherrycorp.com).

Figure 15.4 A typical membrane keyswitch used in NMB keyboards.

Membrane keyboards typically provide a firmer touch than rubber dome keyboards or the old foam-element keyboards, and those with buckling spring designs can provide the ultimate in tactile feedback. One interesting variation includes the line of keyboards made by KeyTronicEMS using its center-bearing version of membrane keyswitches. Most of its keyboards feature Ergo Technology, which has five levels of force from 35 grams to 80 grams, depending on the relative strength of the fingers used to type various keys. As little as 35 grams of force is required for keys that are used by the little finger, such as Q, Z, and A, and greater levels of force are required for keys used by the other fingers (see Figure 15.5). The spacebar requires the most force: 80 grams. This compares to the standard force level of 55 grams for all keys on normal keyboards. For more information about keyboards with Ergo Technology, visit the KeyTronicEMS website (www.keytronic.com).

Figure 15.5 Force levels used on KeyTronicEMS keyboards with Ergo Technology.

Perhaps the most well-known type of membrane keyboards are the IBM/Lexmark “Model M” keyboards, which combine IBM’s legendary buckling spring design with a high-end membrane switch. To find the best membrane keyboards from the vast numbers on the market, look at the lifespan rating of the keyswitches. Longer-lasting keyswitches make the keyboard cost more but will lead to a better experience over the life of the keyboard.

Buckling Spring Capacitive and Membrane Switches

The keyboard included with the original IBM PC, XT, and AT systems used capacitive switches combined with a buckling spring mechanism to provide the ultimate in performance and tactile feedback. Capacitive switches are technically the only truly nonmechanical keyswitches in use today (see Figure 15.6). Although the movement of the key and buckling spring is mechanical in nature, in the original designs these components do not close a mechanical contact or switch. Because of the high cost of the capacitive switches, IBM switched its buckling spring keyboards from capacitive to membrane switches in the mid-1980s. However, unlike more common membrane keyboards, all of the buckling spring keyboards feature extremely high-end designs. Regardless of whether capacitive or membrane designs are used, buckling spring keyswitches are considered to be among the best in the world, offering the highest-quality tactile feedback of any type of switch. They are called buckling spring keyboards because of the coiled spring and rocker used in each keyswitch to provide tactile and audible feedback.

Figure 15.6 A capacitive buckling spring keyswitch.

A capacitive switch does not work by making contact between conductors. Instead, two plates usually made of plastic are connected in a switch matrix designed to detect changes in the capacitance of the circuit. The membrane version of the switch uses upper and lower electrical contact sheets separated by an insulating sheet with small holes.

When a key is pressed, the plunger moves the top plate in relation to the fixed bottom plate, or presses a hammer over the membranes, allowing the top and bottom contacts to touch. The buckling spring mechanism provides for distinct over-center tactile feedback with a resounding “click.” As the capacitance between the two plates changes or the two membranes make contact, the comparator circuitry in the keyboard detects this as a keypress.

The tactile feedback is unsurpassed because the buckling spring design provides a relatively loud click and a strong over-center feel. The only drawback to the design is the cost. Buckling spring keyboards are among the most expensive designs, whether they use capacitive or membrane switches. The quality of the feel and their durability make them worth the price, however.

Although some of IBM’s older keyboards featured capacitive keyswitches, most current IBM/Lenovo keyboards use either membrane, rubber dome, or other lower-cost keyswitches. In 1991, IBM spun off its keyboard/printer division as Lexmark, which then spun off the keyboard division as Unicomp in 1996. Today, Unicomp still manufactures and sells “IBM” keyboards with buckling spring membrane switch (“clickety” as some would say) technology. You can purchase new Unicomp (IBM) keyboards direct by calling the company’s toll-free number (800-777-4886) or by visiting its online store (www.pckeyboard.com).

See “TrackPoint II/III/IV,” p. 829 (this chapter).

The EnduraPro/104 is notable for including a built-in TrackPoint pointing device; however, a design change has rendered the TrackPoint device used in these models as unacceptable. As any TrackPoint user knows, the pointing stick itself is a pressure sensor, not a joystick, and as such it should be rigid and unmovable, Unfortunately, the TrackPoint design now used by Unicomp exhibits unwanted physical movement, greatly reducing the functionality. If you want a keyboard with a TrackPoint, I only recommend IBM or Lenovo models.

Because of the buckling spring keyswitches (and the resulting clickety feel), I am a huge fan of the IBM, Lexmark, and Unicomp keyboards.

The Keyboard Interface

A keyboard consists of a set of switches mounted in a grid or an array called the key matrix. When a switch is pressed, a processor in the keyboard identifies which key is pressed by determining which grid location in the matrix shows continuity. The keyboard processor, which also interprets how long the key is pressed, can even handle multiple keypresses at the same time. A 16-byte hardware buffer in the keyboard can handle rapid or multiple keypresses, passing each one to the system in succession.

When you press a key, the contact bounces slightly in most cases, meaning that several rapid on/off cycles occur just as the switch makes contact. This is called bounce. The processor in the keyboard is designed to filter this, or “debounce” the keystroke. The keyboard processor must distinguish bounce from a double key strike the keyboard operator intends to make. This is fairly easy, though, because the bouncing is much more rapid than a person could simulate by striking a key quickly several times.

The keyboard in a PC is actually a computer itself. It communicates with the main system in one of two ways:

• Through a special serial data link if a standard PS/2 keyboard connector is used

• Through the USB port

The serial data link used by conventional keyboards transmits and receives data in 11-bit packets of information, consisting of 8 data bits, plus framing and control bits. Although it is indeed a serial link (in that the data flows on one wire), the keyboard interface is incompatible with the standard RS-232 serial port commonly used to connect modems.

The processor in the original PC keyboard was an Intel 8048 microcontroller chip. Newer keyboards often use an 8049 version that has built-in ROM or other microcontroller chips compatible with the 8048 or 8049. For example, in its Enhanced keyboards, IBM has always used a custom version of the Motorola 6805 processor, which is compatible with the Intel chips. The keyboard’s built-in processor reads the key matrix, debounces the keypress signals, converts the keypress to the appropriate scan code, and transmits the code to the motherboard. The processors built in to the keyboard contain their own RAM, possibly some ROM, and a built-in serial interface.

In the original PC/XT design, the keyboard serial interface is connected to an 8255 Programmable Peripheral Interface (PPI) chip on the motherboard of the PC/XT. This chip is connected to the interrupt controller IRQ1 line, which is used to signal to the system that keyboard data is available. The data is then sent from the 8255 to the processor via I/O port address 60h. The IRQ1 signal causes the main system processor to run a subroutine (INT 9h) that interprets the keyboard scan code data and decides what to do.

In an AT-type keyboard design, the keyboard serial interface is connected to a special keyboard controller on the motherboard. This controller was an Intel 8042 Universal Peripheral Interface (UPI) slave microcontroller chip in the original AT design. This microcontroller is essentially another processor that has its own 2KB of ROM and 128 bytes of RAM. An 8742 version that uses erasable programmable read-only memory (EPROM) can be erased and reprogrammed. In the past, when you purchased a motherboard ROM upgrade for an older system from a motherboard manufacturer, the upgrade included a new keyboard controller chip as well because it had somewhat dependent and updated ROM code in it. Some older systems might use the 8041 or 8741 chips, which differ only in the amount of built-in ROM or RAM. However, recent systems incorporate the keyboard controller into the main system chipset.

When the keyboard controller on the motherboard receives data from the keyboard, it signals the motherboard with an IRQ1 and sends the data to the main motherboard processor via I/O port address 60h. Acting as an agent between the keyboard and the main system processor, the 8042-type keyboard controller can translate scan codes and perform several other functions as well. The system also can send data to the 8042 keyboard controller via port 60h, which then passes it on to the keyboard. Additionally, when the system needs to send commands to or read the status of the keyboard controller on the motherboard, it reads or writes through I/O port 64h. These commands usually are followed by data sent back and forth via port 60h.

The 8042 keyboard controller is also used by the system to control the A20 memory address line, which provides access to system memory greater than 1MB. More modern motherboards typically incorporate this functionality directly into the motherboard chipset. The AT keyboard connector was renamed the “PS/2” port after the IBM PS/2 family of systems debuted in 1987. That was the time when the connector changed in size from the DIN to the mini-DIN, and even though the signals were the same, the mini-DIN version became known from that time forward as the PS/2 port.

Keyboards connected to a USB port work in a surprisingly similar fashion to those connected to conventional DIN or mini-DIN (PS/2) ports after the data reaches the system. Inside the keyboard a variety of custom controller chips is used by various keyboard manufacturers to receive and interpret keyboard data before sending it to the system via the USB port. Some of these chips contain USB hub logic to enable the keyboard to act as a USB hub. After the keyboard data reaches the USB port on the system, the USB port routes the data to the 8042-compatible keyboard controller, where the data is treated as any other keyboard information.

This process works very well after a system has booted into Windows. But what about users who need to use the keyboard when running an older non-USB aware OS, or within the BIOS configuration routine? That problem is solved by ensuring that USB Legacy support is present and enabled in the BIOS Setup. (See “Advanced USB Configuration Menu,” in Chapter 5 “BIOS”).

Typematic Functions

If a key on the keyboard is held down, it becomes typematic, which means the keyboard repeatedly sends the keypress code to the motherboard. In the AT-style keyboards, the typematic rate is adjusted by sending the appropriate commands to the keyboard processor. This is impossible for the earlier PC/XT keyboard types because the keyboard interface for these types is not bidirectional.

AT-style keyboards have programmable typematic repeat rate and delay parameters. You can adjust the typematic repeat rate and delay parameters with settings in your system BIOS (although not all BIOS chips can control all functions) or in your operating system. In Windows you can use either the MODE command or the Keyboard icon in the Control Panel. Using either method you can set the repeat rate from about 2cps (characters per second) minimum to 30cps maximum, and the delay from 0.25 seconds minimum to 1 second maximum.

For the fastest keyboard operation, I like to set the repeat rate to the maximum (30cps) and the delay to the minimum (0.25 seconds), which can be accomplished with the following command:

MODE CON: RATE=31 DELAY=0

Likewise, slowing the repeat rate to the minimum (2cps) and increasing the delay to the maximum (1 second), can be accomplished with the following command:

MODE CON: RATE=0 DELAY=3

Entering MODE CON: with no other parameters shows the current status of the settings. You can also modify these settings using the Keyboard icon in the Control Panel. The Repeat Delay slider, shown in Figure 15.7, controls the duration for which a key must be pressed before the character begins to repeat, and the Repeat Rate slider controls how fast the character repeats after the delay has elapsed.

Figure 15.7 Setting the keyboard repeat delay and repeat rate in Windows.

The dialog box also contains a text box you can use to test the settings you have chosen before committing them to your system. When you click in the box and press a key, the keyboard reacts using the settings currently specified by the sliders, even if you have not yet applied the changes to the Windows environment.

Keyboard Key Numbers and Scan Codes

When you press a key on the keyboard, the processor built in to the keyboard (8048 or 6805 type) reads the keyswitch location in the keyboard matrix. The processor then sends to the motherboard a serial packet of data containing the scan code for the key that was pressed.

This is called the Make code. When the key is released, a corresponding Break code is sent, indicating to the motherboard that the key has been released. The Break code is equivalent to the Make scan code plus 80h. For example, if the Make scan code for the “A” key is 1Eh, the Break code would be 9Eh. By using both Make and Break scan codes, the system can determine whether a particular key has been held down and determine whether multiple keys are being pressed.

In motherboards that use an 8042-type keyboard controller, the 8042 chip translates the actual keyboard scan codes into one of up to three sets of system scan codes, which are sent to the main processor. It can be useful in some cases to know what these scan codes are, especially when you’re troubleshooting keyboard problems or when reading the keyboard or system scan codes directly in software.

When a keyswitch on the keyboard sticks or otherwise fails, the Make scan code of the failed keyswitch usually is reported by diagnostics software, including the power-on self test (POST), as well as conventional disk-based diagnostics. This means you must identify the malfunctioning key by its scan code. See the Technical Reference section of the disc included with this book for a comprehensive listing of keyboard key numbers and scan codes for industry-standard 101/102-key (Enhanced) and 104-key Windows keyboards. By looking up the reported scan code on these charts, you can determine which keyswitch is defective or needs to be cleaned.

IBM originally assigned each key a unique key number to distinguish it from the others. This is helpful when you are trying to identify keys on foreign keyboards that might use symbols or characters different from what the U.S. models do. In the Enhanced keyboard, most foreign models are missing one of the keys (key 29) found on the U.S. version and have two additional keys (keys 42 and 45). This accounts for the 102-key total instead of the 101 keys found on the U.S. version.

Many keyboards feature hotkeys that either have fixed uses—such as opening the default web browser, sending the system into standby mode, and adjusting the speaker volume—or are programmable for user-defined functions. Each of these keys also has scan codes. USB keyboards use a special series of codes called Human Interface Device (HID), which are translated into PS/2 scan codes.

International Keyboard Layouts

After the keyboard controller in the system receives the scan codes generated by the keyboard and passes them to the main processor, the operating system converts the codes into the appropriate alphanumeric characters. In the United States, these characters are the letters, numbers, and symbols found on the standard American keyboard.

However, no matter which characters you see on the keytops, adjusting the scan code conversion process to map different characters to the keys is relatively simple. Windows takes advantage of this capability by enabling you to install multiple keyboard layouts to support various languages, through the Region and Language Options applet in the Windows Control Panel.

These keyboard layouts map various characters to certain keys on the standard keyboard. The standard French layout provides easy access to the accented characters commonly used in that language. For example, pressing the 2 key produces the é character. To type the numeral 2, you press the Shift+2 key combination. Other French-speaking countries have different keyboard conventions for the same characters, so Windows includes support for several keyboard layout variations for some languages, based on nationality.

The alternative keyboard layouts also do not provide support for non-Roman alphabets, such as Russian and Chinese. The accented characters and other symbols used in languages such as French and German are part of the standard ASCII character set. They are always accessible to English-language users through the Windows Character Map utility or through the use of Alt+keypad combinations. An alternative keyboard layout simply gives you an easier way to access the characters used in certain languages.

If you work on documents using more than one language, you can install as many keyboard layouts as necessary and switch between them at will. Using the settings in the Regional and Language Options applet, you can enable both a selector in the taskbar notification area as well as a key combination that switches between the installed keyboard layouts.

Keyboard/Mouse Interface Connectors

Keyboards typically have a cable with one of three primary types of connectors at the system end. On most aftermarket keyboards, the cable is connected inside the keyboard case on the keyboard end, requiring you to open the keyboard case to disconnect or test it; different vendors use different connections, making cable interchange between brands of keyboards unlikely. When IBM manufactured its own enhanced keyboards, it used a unique cable assembly that plugged into both the keyboard and the system unit to make cable replacement or interchange easy. Current IBM keyboards, unfortunately, no longer use either the shielded data link (SDL) connector inside the keyboard or the telephone cable-style removable plug-in external keyboard connector used on some more recent models.

Although the method of connecting the keyboard cable to the keyboard can vary (some even use wireless connections), all PC keyboards use one of the following three connectors to interface the keyboard (or wireless transceiver) to the computer:

• 5-pin DIN connector—Used on most obsolete PC systems with Baby-AT form factor motherboards.

• 6-pin mini-DIN connector—Often called a PS/2 connector because it was first used on IBM PS/2 systems.

• USB connector—Most recent systems use USB keyboards and mice.

Figure 15.8 and Table 15.2 show the physical layout and pinouts of the respective keyboard connector plugs and sockets (except USB); although the 6-pin SDL connector is not used in this form by most keyboard vendors, most non-IBM keyboards use a somewhat similar connector to attach the keyboard cable to the inside of the keyboard. You can use the pinouts listed in Table 15.2 to test the continuity of each wire in the keyboard connector.

Figure 15.8 Keyboard and mouse connectors.

Table 15.2 Keyboard Connector Signals and Specifications

PS/2 mouse devices also use the 6-pin mini-DIN connector and have the same pinout and signal descriptions as the keyboard connector; however, the data packets are incompatible. Therefore, you can easily plug a motherboard mouse (PS/2-style) into a mini-DIN keyboard connector or plug the mini-DIN keyboard connector into a motherboard mouse port. Neither one will work properly in this situation, though.

USB keyboards use the Series A USB connector to attach to the USB port built into modern computers. For more information on USB, refer to Chapter 14, “External I/O Interfaces.”

USB Keyboards

Most keyboards now on the market connect to the PC via a USB port instead of the standard PS/2 keyboard port. Because USB is a universal bus that uses a hub to enable multiple devices to connect to a single port, a single USB port in a system can replace the standard serial and parallel ports as well as the keyboard and mouse ports. Many systems and motherboards still include the standard PS/2 keyboard and mouse ports (now called legacy ports) as well as USB, but many newer legacy-free systems and replacement motherboards have only USB ports for interfacing external devices.

Most keyboard manufacturers now market USB keyboards, but if you want to use your keyboard with both legacy (PS/2) and legacy-free (USB) systems, the most economic way to do so is to specify a keyboard that includes both a USB connector and an adapter to permit the keyboard to work with PS/2 ports.

Although rare in modern systems, some older systems don’t accept USB keyboards, even those with USB ports, because the standard PC BIOS has a keyboard driver that expects a standard keyboard port interface to be present. When a USB keyboard is installed on a system that lacks USB keyboard support, the system can’t use it because no driver exists in the BIOS to make it work. In fact, some systems see the lack of a standard keyboard as an error and halt the boot process until one is installed.

To use a keyboard connected via the USB port, you must meet three requirements:

• Have a USB port in the system.

• Run Microsoft Windows 98 or newer (previous versions did not include USB keyboard drivers).

• Have a system chipset and BIOS that feature USB Legacy (keyboard and mouse) support.

USB Legacy support means your motherboard has a chipset and ROM BIOS drivers that enable a USB keyboard to be used outside the Windows GUI environment. Almost all 1998 and newer systems with USB ports include a chipset and BIOS with USB Legacy (meaning USB Keyboard) support, although it might be disabled by default in the system BIOS.

Even though USB Legacy support enables you to use a USB keyboard in almost all situations, don’t scrap your standard-port keyboards just yet. If the system has PS/2 keyboard and mouse ports, they may need to be used when running hardware diagnostics, flashing the motherboard ROM BIOS, or troubleshooting USB keyboard and mouse issues. I’ve also had to use PS/2 keyboards and mice when installing older Windows versions on newer systems, due to the lack of proper support until the chipset USB drivers are installed. A good PC tech will always have PS/2 keyboards and mice on hand for testing.

If you have problems with USB keyboards and mice (USB Legacy support), look at these possible solutions:

• Microsoft’s Knowledge Base (http://support.microsoft.com) might have an article that addresses your problem.

• Your keyboard or mouse vendor might offer new drivers.

• Your system or motherboard manufacturer might have a BIOS upgrade you can install.

• As a fallback, connect the keyboard to the PS/2 port with an adapter, or use a PS/2 keyboard and mouse until you resolve the problem.

See “Universal Serial Bus (USB),” p. 766 (Chapter 14).

Keyboards with Special Features

Several keyboards on the market have special features not found in standard designs. These additional features range from simple things, such as built-in calculators, clocks, and volume control, to more complicated features, such as integrated pointing devices, special character layouts, power management keys, special shapes, internal lighting, and even user-customizable or programmable keys.

Ergonomic Keyboards

A trend that began in the late 1990s is to change the shape of the keyboard instead of altering the character layout. This trend has resulted in several so-called ergonomic designs. The goal is to shape the keyboard to better fit the human hand. The most common of these designs splits the keyboard in the center, bending the sides outward. Some designs allow the angle between the sides to be adjusted, while others are fixed. The split or bent designs more easily conform to the hands’ natural angles while typing than the standard keyboard. They can improve productivity and typing speed and help prevent repetitive strain injuries (RSI), such as carpal tunnel syndrome (tendon inflammation). A good source for highly ergonomic keyboards, pointing devices, and furniture is Ergonomic Resources (www.ergonomicsmadeeasy.com).

Because of their novelty and trendy appeal, some ergonomic keyboards can be considerably more expensive than traditional designs, but for users with medical problems caused or exacerbated by improper positioning of the wrists at the keyboard, they can be an important remedy to a serious problem. General users, however, are highly resistant to change, and these designs have yet to significantly displace the standard keyboard layout. If you don’t want to spend big bucks on the more radical ergonomic keyboards but want to give yourself at least limited protection from RSI, consider keyboards with a built-in wrist rest or add a gel-based wrist rest to your current keyboard. These provide hand support without making you learn a modified or brand-new keyboard layout.

Keyboard Troubleshooting and Repair

Keyboard errors are usually caused by two simple problems. Other more difficult, intermittent problems can arise, but they are much less common. The most frequent problems are as follows:

• Defective cables

• Stuck keys

Many older keyboards, such as the heavy-duty units made by IBM, had replaceable cables. Defective cables are easy to spot if the failure is not intermittent. If the keyboard stops working altogether or every keystroke results in an error or incorrect character, the cable is likely the culprit. Troubleshooting is simple if your keyboard has a detachable cable, especially if you have a spare cable on hand. Simply replace the suspected cable with one from a known, working keyboard to verify whether the problem still exists. If it does, the problem must be elsewhere.

Most modern keyboards have nonreplaceable cables, at least from the outside. In some cases you can open up the keyboard case, and you will see that the cable is internally connected via a removable plug. Unfortunately, those cables are not sold separately, meaning that the only source for one would be from another keyboard, making a replacement implausible.

If the cable is removable, you can test it for continuity with a digital multimeter (DMM). DMMs that have an audible continuity tester built in make this procedure much easier to perform. To test each wire of the cable, insert the DMM’s red pin into the keyboard connector and touch the DMM’s black pin to the corresponding wire that attaches to the keyboard’s circuit board. Wiggle the ends of the cable as you check each wire to ensure no intermittent connections exist. If you discover a problem with the continuity in one of the wires, replace the cable or the entire keyboard, whichever is cheaper. Because replacement keyboards are so inexpensive, it’s almost always cheaper to replace the entire unit than to get a new cable, unless the keyboard is an expensive unit like an older IBM Model M. You can get replacement cables (and other parts) for older IBM Model M type keyboards from www.clickykeyboards.com.

For more information about using digital multimeters for testing hardware, see Chapter 20, “PC Diagnostics, Testing, and Maintenance.”

Many times you first discover a problem with a keyboard because the system has an error during the POST. Many systems use error codes in a 3xx numeric format to distinguish the keyboard. If you encounter any such errors during the POST, write them down. Some BIOS versions do not use cryptic numeric error codes; they simply state something such as the following:

Keyboard stuck key failure

This message is usually displayed by a system with a Phoenix BIOS if a key is stuck. Unfortunately, the message does not identify which key it is!

If your system displays a 3xx (keyboard) error preceded by a two-digit hexadecimal number, the number is the scan code of a failing or stuck keyswitch. Look up the scan code in the tables provided in the Technical Reference section on the disc to determine which keyswitch is the culprit. By removing the keycap of the offending key and cleaning the switch, you often can solve the problem.

For a simple test of the motherboard keyboard connector, you can check voltages on some of the pins. Using Figure 15.8 (shown earlier in the chapter) as a guide, measure the voltages on various pins of the keyboard connector. To prevent possible damage to the system or keyboard, turn off the power before disconnecting the keyboard. Then, unplug the keyboard and turn the power back on. Make measurements between the ground pin and the other pins according to Table 15.2, shown earlier in the chapter. If the voltages are within these specifications, the motherboard keyboard circuitry is probably okay.

If your measurements do not match these voltages, the motherboard might be defective. Otherwise, the keyboard cable or keyboard might be defective. If you suspect that the keyboard and/or cable is the problem, the easiest thing to do is to connect a known-good keyboard as a test. If the system works properly with the known-good keyboard, then you know the original keyboard and/or cable is defective. If the system still does not work normally, you might have to replace the motherboard.

In many newer systems, the motherboard’s keyboard and mouse connectors are protected by a fuse that can be replaced. Look for any type of fuse on the motherboard in the vicinity of the keyboard or mouse connectors. Other systems might have a socketed keyboard controller chip (8042-type). In that case, you might be able to repair the motherboard keyboard circuit by replacing this chip. Because these chips have ROM code in them, you should get the replacement from the motherboard or BIOS manufacturer. If the motherboard uses a soldered keyboard controller chip or a chipset that integrates the keyboard controller with other I/O chips, you’ll need to replace the motherboard.

See the disc included with this book for a listing of the standard POST and diagnostic keyboard error codes used by some systems.

Keyboard Disassembly

Although disassembling a keyboard is possible, most likely you won’t need or want to do that given how inexpensive new keyboards have become. If you do want to disassemble your keyboard, see “Keyboard Disassembly” in the Technical Reference section of the disc accompanying this book.

Cleaning a Keyboard

One of the best ways to keep a keyboard in top condition is periodic cleaning. As preventive maintenance, you should vacuum the keyboard weekly, or at least monthly. When vacuuming, you should use a soft brush attachment; this will help dislodge the dust. Also note that many keyboards have keycaps that can come off easily. Be careful when vacuuming; otherwise, you’ll have to dig them out of the vacuum cleaner. I recommend using a small, handheld vacuum cleaner made for cleaning computers and sewing machines; these have enough suction to get the job done with little risk of removing your keytops.

You also can use canned compressed air to blow the dust and dirt out instead of using a vacuum. Before you dust a keyboard with the compressed air, turn the keyboard upside down so that the particles of dirt and dust collected inside can fall out.

On all keyboard, each keycap is removable, which can be handy if a key sticks or acts erratically. For example, a common problem is a key that does not work every time you press it. This problem usually results from dirt collecting under the key. An excellent tool for removing keycaps on almost any keyboard is the U-shaped chip puller included in many computer tool kits. Simply slip the hooked ends of the tool under the keycap, squeeze the ends together to grip the underside of the keycap, and lift up. IBM sells a tool designed specifically for removing keycaps from its keyboards, but the chip puller works even better. After removing the cap, spray some compressed air into the space under the cap to dislodge the dirt. Then replace the cap and check the action of the key.

When you remove the keycap on some keyboards, you are actually detaching the entire key from the keyswitch. Be careful during the removal or reassembly of the keyboard; otherwise, you’ll break the switch. The classic IBM/Lexmark-type Model M keyboards (now made by Unicomp) use a removable keycap that leaves the actual key in place, enabling you to clean under the keycap without the risk of breaking the switches. If your keyboard doesn’t have removable keycaps, consider using cleaning wands with soft foam tips to clean beneath the keytops.

Spills can be a problem, too. If you spill a soft drink or cup of coffee into a keyboard, you do not necessarily have a disaster. Many keyboards that use membrane switches are spill resistant. However, you should immediately (or as soon as possible) disconnect the keyboard and flush it out with distilled water. Partially disassemble the keyboard and use the water to wash the components. (See “Keyboard Disassembly” in the Technical Reference section of the disc accompanying this book for disassembly instructions.) If the spilled liquid has dried, soak the keyboard in some of the water for a while. When you are sure the keyboard is clean, pour another gallon or so of distilled water over it and through the keyswitches to wash away any residual dirt. After the unit dries completely, it should be perfectly functional. You might be surprised to know that drenching your keyboard with water does not harm the components. Just make sure you use distilled water, which is free from residue or mineral content. (Bottled water is not distilled; the distinct taste of many bottled waters comes from the trace minerals they contain!) Also, make sure the keyboard is fully dry before you try to use it; otherwise, some of the components might short out. Some have even put keyboards in a dishwasher (top rack, no detergent) in order to clean them, and with good results.

Keyboard Recommendations

Many of the keyboards supplied with lower-cost PCs leave much to be desired. They often have a mushy feel, with little or no tactile feedback. A poor keyboard can make using a system a frustrating experience, especially if you are a touch typist. For all these reasons, it is often a good idea to replace an existing keyboard with something better.

Perhaps the highest-quality keyboards in the entire computer industry are the “Model M” buckling spring keyswitch designs originally made by IBM (or, more accurately today, Unicomp). Unicomp maintains an extensive selection of more than 1,400 Lexmark and IBM keyboard models and continues to develop and sell a wide variety of traditional and customized models, including keyboards that match the school colors of several universities. Unicomp sells keyboards directly via its website at www.pckeyboard.com. Another great source for IBM keyboards is www.clickykeyboard.com, which offers a number of used and even new-old stock keyboards, including those with integral TrackPoints.

If you are a ThinkPad user and love the TrackPoint and UltraNav (TrackPoint with scroll button plus touchpad), you can get an actual ThinkPad UltraNav keyboard in both standard and portable (without numeric keypad) designs:

• ThinkPad Full-Size UltraNav USB Keyboard—P/N 31P8950

• ThinkPad Travel UltraNav USB Keyboard—P/N 31P9490

The “travel” version lacks the numeric keypad included on the full-size version, and also includes a carrying case. Both include a built-in USB hub with two ports on the keyboard for attaching additional USB devices such as a conventional mouse. They also have a built-in cord wrap that allow you to adjust the length of the cord as well as to hide it completely for storage. Although they don’t have the heavy feel of the buckling spring keyswitch design, they do have the same high-quality keyboards as the legendary ThinkPad laptops, and include the exact same UltraNav TrackPoint pointing device as well. They are both extremely light in weight: The travel version weighs only 1.17 lbs, whereas the full-size model weighs only 1.41 lbs. You can get them from most places that sell ThinkPad accessories. A good way to find the best price is to search for the part numbers online; you can usually find them for between $40 and $99. Using these keyboards makes the transition from laptop to desktop easy, because you can have the same keyboard and pointing devices on both.

Other excellent keyboards include the revived Northgate designs sold under the Avant Prime and Avant Stellar names by Creative Vision Technologies. These keyboards have excellent tactile feedback, with a positive click sound.

Pointing Devices

The mouse was invented in 1964 by Douglas Engelbart, who at the time was working at the Stanford Research Institute (SRI), a think tank sponsored by Stanford University. The mouse was officially called an X-Y Position Indicator for a Display System. Xerox later applied the mouse to its revolutionary Alto computer system in 1973. At the time, unfortunately, these systems were experimental and used purely for research.

In 1979, several people from Apple—including Steve Jobs—were invited to see the Alto and the software that ran the system. Steve Jobs was blown away by what he saw as the future of computing, which included the use of the mouse as a pointing device and the graphical user interface (GUI) it operated. Apple promptly incorporated these features into what was to become the Lisa computer and lured away 15–20 Xerox scientists to work on the Apple system.

Although Xerox released the Star 8010 computer, which used this technology, in 1981, it was expensive, poorly marketed, and perhaps way ahead of its time. Apple released the Lisa computer, its first system that used the mouse, in 1983. It was not a runaway success, largely because of its $10,000 list price, but by then Jobs already had Apple working on the low-cost successor to the Lisa: the Macintosh. The Apple Macintosh was introduced in 1984. Although it was not an immediate hit, the Macintosh has grown in popularity since that time.

Many credit the Macintosh with inventing the mouse and GUI, but as you can see, this technology was actually borrowed from others, including SRI and Xerox. Certainly Microsoft Windows has popularized this interface and brought it to the legion of Intel-based PC systems.

Although the mouse did not catch on quickly in the PC marketplace, today the GUIs for PC systems, such as Windows, practically demand the use of a mouse. Therefore, virtually every new system sold at retail comes with a mouse. And, because the mice packaged with retail systems are seldom high-quality or up-to-date designs, sooner or later most users are in the market for a better mouse or compatible pointing device.

Mice come in many shapes and sizes from many manufacturers. Some have taken the standard mouse design and turned it upside down, creating the trackball. In the trackball devices, you move the ball with your hand directly rather than moving the unit itself. Trackballs were originally found on arcade video games, such as Missile Command, and are popular with users who have limited desk space. In most cases, the dedicated trackballs have a much larger ball than would be found on a standard mouse. Other than the orientation and perhaps the size of the ball, a trackball is identical to a mouse in design, basic function, and electrical interface. Like many recent mice, trackballs often come in ergonomic designs, and the more recent models even use the same optical tracking mechanisms used by the latest Microsoft and Logitech mice.

The largest manufacturers of mice are Microsoft and Logitech; these two companies provide designs that inspire the rest of the industry and each other and are popular OEM choices as well as retail brands. Even though mice can come in different varieties, their actual use and care differ very little. The standard mouse consists of several components:

• A housing that you hold in your hand and move around on your desktop.

• A method of transmitting movement to the system: either ball/roller or optical sensors.

• Buttons (two or more, and often a wheel or toggle switch) for making selections.

• Wheel for vertical scrolling. Some wheels tilt for horizontal scrolling and/or can be pressed to act as a button.

• An interface for connecting the mouse to the system. Conventional mice use a wire and connector, whereas wireless mice use a radio-frequency or infrared transceiver in both the mouse and a separate unit connected to the computer to interface the mouse to the computer.

The housing, which is made of plastic, consists of very few moving parts. On top of the housing, where your fingers normally rest, are buttons. There might be any number of buttons, but mice designed for PCs have always had two buttons, and since 1996 a scroll wheel as well. Although the latest versions of Windows support scrolling mice, other features supported by the vendor, including additional buttons, still require installing the vendor’s own mouse driver software.

Ball-Type Mice

The bottom of the mouse housing is where the detection mechanisms or electronics are located. On traditional mice, the bottom of the housing contains a small, rubber ball that rolls as you move the mouse across the tabletop. The movements of this rubber ball are translated into electrical signals transmitted to the computer across the cable.

Internally, a ball-driven mouse is very simple, too. The ball usually rests against two rollers: one for translating the x-axis movement and the other for translating the y-axis movement. These rollers are typically connected to small disks with shutters that alternately block and allow the passage of light. Small optical sensors detect movement of the wheels by watching an internal infrared light blink on and off as the shutter wheel rotates and “chops” the light. These blinks are translated into movement along the axes (see Figure 15.9). Figure 15.10 shows a PS/2 mouse connector.

Figure 15.9 Typical opto-mechanical mouse mechanism.

Figure 15.10 Typical PS/2-type mouse connector.

Optical Mice

The other major method of motion detection is optical. Some of the early mice made by Mouse Systems and a few other vendors used a sensor that required a special grid-marked pad. Although these mice were very accurate, the need to use them with a pad caused them to fall out of favor.

Microsoft’s IntelliMouse Explorer pioneered the rebirth of optical mice. The IntelliMouse Explorer and the other new-style optical mice from Logitech and other vendors use optical technology to detect movement, and they have no moving parts of their own (except for the scroll wheel and buttons on top). Today’s optical mice need no pad; they can work on virtually any surface. This is done by upgrading the optical sensor from the simple type used in older optical mice to a more advanced CCD (charge coupled device). This essentially is a crude version of a video camera sensor that detects movement by seeing the surface move under the mouse. An LED or diode laser is used to provide light for the sensor.

The IntelliMouse Explorer revolutionized the mouse industry; first Logitech, then virtually all other mouse makers, including both retail and OEM suppliers, have moved to optical mice for most of their product lines, offering a wide variety of optical mice in most price ranges. Figure 15.11 shows the essential features of a typical optical mouse.

Figure 15.11 The bottom of the Logitech iFeel optical mouse.

Their versatility and low maintenance (not to mention that neat red or blue glow out the sides!) make optical mice an attractive choice, and the variety of models available from both vendors means you can have the latest optical technology for about the price of a good ball-type mouse. Figure 15.12 shows the interior of a typical optical mouse.

Figure 15.12 The LED inside an optical mouse illuminates the surface by blinking many times per second. The light is reflected from the mousing surface back to the sensor, which converts the information into digital form and sends it to the computer.

All optical mice have a resolution of at least 400 dpi. However, for better performance, some optical mice have adjustable sensors that offer up to 2,000 dpi resolution or even higher. These are often sold as gaming mice because the higher resolution offers faster response for quick game movements. Many mice now incorporate infrared laser technology sensors, which increase the resolution of the sensor, allowing for improved tracking on glossy or transparent surfaces.

Optical mice are available as corded or wireless models, which use either infrared or RF transceivers to replace the cable. A receiver is plugged into the USB or mouse port, and the battery-powered mouse contains a compatible transmitter. Wireless ball-type mice are usually much larger than ordinary mice because of the need to find room for both the bulky ball mechanism and batteries, but wireless optical mice are about the same size as high-end corded mice.

After the mouse is connected to your computer, it communicates with your system through the use of a device driver, which can be loaded explicitly or built into the operating system software. For example, no separate drivers are necessary to use a mouse with modern operating systems such as Windows, but using the mouse with older operating systems such as DOS requires a separate driver to be loaded from the CONFIG.SYS or AUTOEXEC.BAT file. Regardless of whether it is built in, the driver translates the electrical signals sent from the mouse into positional information and indicates the status of the buttons.

The standard mouse drivers in Windows are designed for the traditional two-button mouse or scroll mouse (in Windows Me or later), but increasing numbers of mice feature additional buttons, toggles, or wheels to make them more useful. These additional features require special mouse driver software supplied by the manufacturer.

Pointing Device Interface Types

The connector used to attach your mouse to the system depends on the type of interface you are using. Mice are most commonly connected to your computer through the following interfaces:

• Serial interface (obsolete)

• Dedicated motherboard (PS/2) mouse port

• USB port

• Bluetooth/wireless (transceiver connected via USB)

Serial

A popular method of connecting a mouse to older PCs is through the standard serial interface. As with other serial devices, the connector on the end of the mouse cable is typically a 9-pin female connector; some very old mice used a 25-pin female connector. Only a couple of pins in the DB-9 or DB-25 connector are used for communications between the mouse and the device driver, but the mouse connector typically has all 9 or 25 pins present.

Because most older PCs come with two serial ports, a serial mouse can be plugged into either COM1 or COM2. The device driver, when initializing, searches the ports to determine to which one the mouse is connected. Some mouse drivers can’t function if the serial port is set to COM3 or COM4, but most can work with any COM port (1–4).

Because a serial mouse does not connect to the system directly, it does not use system resources by itself. Instead, the resources are those used by the serial port to which it is connected. For example, if you have a mouse connected to COM2, and if COM2 is using the default IRQ and I/O port address range, both the serial port and the mouse connected to it use IRQ3 and I/O port addresses 2F8h–2FFh.

See “Serial Ports,” p. 791 (Chapter 14).

Motherboard Mouse Port (PS/2)

Most computers include a dedicated mouse port built into the motherboard. This practice was introduced by IBM with the PS/2 systems in 1987, so this interface is often referred to as a PS/2 mouse interface. This term does not imply that such a mouse can work only with a PS/2; instead, it means the mouse can connect to any system that has a dedicated mouse port on the motherboard.

From a hardware perspective, a motherboard mouse connector is usually exactly the same as the mini-DIN connector used for keyboards. In fact, the motherboard mouse port is connected to the 8042-type keyboard controller found on the motherboard. All the PS/2 computers include mini-DIN keyboard and mouse port connectors on the back. Most computers based on the semiproprietary LPX motherboards and all ATX-series motherboards use these same connectors for space reasons. Most Baby-AT motherboards have a pin-header-type connector for the mouse port because most standard cases do not have a provision for the mini-DIN mouse connector. If that is the case, an adapter cable is usually supplied with the system. This cable adapts the pin-header connector on the motherboard to the standard mini-DIN type connector used for the motherboard mouse.

Connecting a mouse to the built-in mouse port is the best method of connection on systems that don’t have USB ports because you do not sacrifice any of the system’s interface slots or any serial ports, and the performance is not limited by the serial port circuitry. The standard resource usage for a motherboard (or PS/2) mouse port is IRQ12, as well as I/O port addresses 60h and 64h. Because the motherboard mouse port uses the 8042-type keyboard controller chip, the port addresses are those of this chip. IRQ12 is an interrupt that is usually free on most systems, but if you use a USB mouse, you can probably disable the mouse port to make IRQ12 available for use by another device.

Hybrid Mice

Hybrid mice are those designed to plug into two types of ports. Although a few low-cost mice sold at retail are designed to plug into either the serial port or the PS/2 port, most mice on the retail market today are designed to plug into either the PS/2 port or the USB port. These combination mice are more flexible than the mice typically bundled with systems, which are designed to work only with the PS/2 or USB port to which they attach.

Circuitry in a hybrid mouse automatically detects the type of port to which it is connected and configures the mouse automatically. Serial-PS/2 hybrid mice usually come with a mini-DIN connector on the end of their cable and an adapter that converts the mini-DIN to a 9- or 25-pin serial port connector, although the reverse is sometimes true on early examples of these mice. PS/2-USB mice usually come with the USB connector on the end of their cable and include a mini-DIN (PS/2) adapter, as shown in Figure 15.13.

Figure 15.13 A typical USB mouse with a PS/2 adapter.

Sometimes people use adapters to try to connect a serial mouse to a motherboard mouse port or a motherboard mouse to a serial port. If this does not work, it is not the fault of the adapter. If the mouse does not explicitly state that it is both a serial and a PS/2-type mouse, it works only on the single interface for which it was designed. Most of the time, you find the designation for which type of mouse you have printed on its underside. A safe rule of thumb to follow is if the mouse didn’t come with an adapter or come bundled with a system, it probably won’t work with an adapter.

USB

The extremely flexible USB port has become the most popular port to use for mice as well as keyboards and other I/O devices. Compared to the other interfaces, USB mice (and other USB pointing devices such as trackballs) have the following advantages:

• USB mice move much more smoothly than the traditional PS/2 type. This is because the frequency with which the mouse reports its position is much higher. A typical PS/2 mouse has a reporting rate of about 40Hz, whereas an average USB-wired mouse has a reporting rate of 125Hz (most USB wireless mice have a reporting rate of 40Hz–50Hz). Several utilities are available to test and adjust the mouse frequency.

• USB mice and pointing devices, similar to all other USB devices, are hot-swappable. If you like to use a trackball and your computing partners prefer mice, you can just lean over and unplug the other users’ pointing device and plug in your own, or move it from PC to PC. You can’t do that with the other port types.

• Multiple pointing devices. With USB, you can easily have multiple pointing devices connected simultaneously, and easily switch between them or use them together in collaboration.

• USB mice can be attached to a USB hub. Using a hub makes attaching and removing your mouse easy without crawling around on the floor to reach the back of the computer. Many computers have front-mounted USB ports, letting you easily attach and remove a USB mouse without the use of an external hub.

Although the early USB mice were decidedly on the premium end of the price scale, low-cost USB mice are now available for as little as $10. That said, plenty of optical and laser mice are available with premium prices up to $100 and more.

If you want to use a USB mouse at an MS-DOS prompt, in Windows Safe mode, or in some other environment outside of normal Windows 98 or later, make sure that USB Legacy mode is enabled in your PC’s BIOS, as discussed earlier in this chapter. Legacy mode enables non-USB-aware systems to recognize a USB keyboard and mouse.

A fourth type of connection, the bus mouse (referred to by Microsoft as the Inport mouse), used a dedicated ISA bus adapter card and is considered long obsolete.

Mouse Troubleshooting

If you are experiencing problems with your mouse, you need to look in only two general places—hardware and software. Because mice are basically simple devices, looking at the hardware takes very little time. Detecting and correcting software problems can take a bit longer, however.

If your system refuses to recognize the mouse, try using a different mouse that you know works. If that doesn’t resolve the problem, then the port you are connecting the mouse to might be bad. If the mouse is connected via USB, then try a different USB port. If a motherboard-based PS/2 mouse port goes bad, you can replace the entire motherboard—which is usually expensive—or you can just use a USB mouse instead.

I have had problems in which a bad PS/2 interface mouse caused the system to lock right as the driver loaded or when third-party diagnostics were being run on the system. Try unplugging the mouse to see if the system will boot; if it does, then the mouse or PS/2 mouse port (meaning the motherboard) may be the problem.

To troubleshoot wireless mice, see “Troubleshooting Wireless Input Devices,” later in this chapter.

Cleaning Your Mouse

If you notice that the mouse pointer moves across the screen in a jerky fashion, it might be time to clean your mouse. For a mouse with a roller-ball, this jerkiness is caused when dirt and dust become trapped around the mouse’s ball-and-roller assembly, thereby restricting its free movement.

From a hardware perspective, the mouse is a simple device, so cleaning it is easy. The first step is to turn the mouse housing over so that you can see the ball on the bottom. Notice that surrounding the ball is an access panel you can open. Sometimes instructions indicate how the panel is to be opened. (Some off-brand mice might require you to remove some screws to get at the roller ball.) Remove the panel to see more of the roller ball and the socket in which it rests.

If you turn the mouse back over, the rubber roller ball should fall into your hand. Take a look at the ball. It might be gray or black, but it should have no visible dirt or other contamination. If it does, wash it in soapy water or a mild solvent, such as contact lens cleaner solution or alcohol, and dry it off.

Now take a look at the socket in which the roller ball normally rests. You will see two or three small wheels or bars against which the ball usually rolls. If you see dust or dirt on or around these wheels or bars, you need to clean them. The best way is to use a compressed air duster, which can blow out any dust or dirt. You also can use some electrical contact cleaner to clean the rollers. Remember, any remaining dirt or dust impedes the movement of the roller ball and results in the mouse not working as it should.

Put the mouse back together by inserting the roller ball into the socket and then securely attaching the cover panel. The mouse should look just as it did before you removed the panel, except that it will be noticeably cleaner.

One of the major advantages of the new breed of optical mice is the lack of moving parts. Just wipe away dust from the optical sensor, and that’s all the cleaning an optical mouse needs.

Scroll Wheels

Late in 1996, Microsoft introduced the IntelliMouse, which differed from standard Microsoft mice by adding a small gray wheel between the mouse buttons. Although this was not technically the first scrolling mouse on the market (Mouse Systems introduced the ProAgio and Genius EasyScroll in 1995), it was the first to have widespread support. Since then, Logitech, IBM, and virtually all other mouse vendors have made scroll wheels or similar devices compatible with the Microsoft design as standard across almost all models, including OEM mice bundled with computer systems.

The wheel has two main functions. The primary function is to act as a scrolling device, enabling you to scroll through documents or web pages by manipulating the wheel with your index finger. The wheel also functions as a third mouse button when you press it.

Each vendor’s mouse driver software offers unique features to enhance the basic operation of the mouse. For example, Logitech’s MouseWare drivers enable you to select which function the OS should perform when you click one of the mouse’s extra buttons. The drivers also provide various options for how to scroll with each wheel click (three lines, six lines, or one screen). Microsoft’s IntelliMouse driver offers a feature called ClickLock, which allows you to drag items without holding down the primary mouse button. In addition, it offers a Universal Scroll feature that adds scrolling mouse support to applications that lack such support. To get the most from whatever scrolling or other advanced-feature mouse you have, be sure you use the latest mouse drivers for your specific make and model.

TrackPoint II/III/IV

On October 5, 1992, IBM introduced a revolutionary new pointing device called TrackPoint as an integrated feature of its new ThinkPad 700 and 700C computers. Often referred to as a pointing stick, the TrackPoint appears as a small rubber cap on the keyboard just above the B key, and between the G and H keys. This was in my opinion the most significant new pointing device since the mouse was invented nearly 30 years earlier!

The TrackPoint device occupies no space on a desk, does not have to be adjusted for left-handed or right-handed use, has no moving parts to fail, and (most importantly) does not require you to move your hands from the home row to use it. This is an absolute boon for touch typists.

I was fortunate enough to meet the actual creator of this device in early 1992 at the spring Comdex/Windows World show in Chicago. While attending the show I had stumbled upon a gentleman wearing suspenders and sporting a pony-tail in a small corner of the IBM booth. His appearance piqued my interest because he was clearly not a “suit,” but instead looked to be some sort of scientist or engineer. I was right, and he was there showing off custom-made prototype keyboards with a small stick in the middle. The stick was covered with a soft cream-colored silicone rubber coating that allowed you to press on the stick without your finger slipping off. In fact, he told me that these were hand-built prototypes he had installed in standard desktop keyboards, and that he was there trying to get public reaction and feedback on the invention. I was invited to play with one of the keyboards, which was connected to a demonstration system. I found that by pressing on the stick with my index finger, I could easily move the mouse pointer around on the screen. The stick itself did not move (it was not a joystick). Instead, it was connected to pressure transducers that measured the amount and direction of the force applied by my finger, and moved the mouse pointer accordingly. The harder I pressed, the faster the pointer moved. After playing around for just a few minutes, the pointer movements became automatic—almost as though I could just “think” about where I wanted the pointer to go, and it would go there.

The gentleman at the booth turned out to be Dr. Ted Selker, the primary inventor of the device. He and Joseph Rutledge created this integrated pointing device at the IBM T.J. Watson Research Center. When I asked him when such keyboards would become available, he could not answer—at the time there were apparently no plans for production, and he was only trying to test user reaction to the device. I filled out one of the survey forms, indicating that I was extremely interested in the revolutionary device and would gladly purchase one if they became available in the future.

Well, the feedback must have helped, because just over six months later, IBM had announced the ThinkPad 700, which included this revolutionary device—then known as the TrackPoint II. Since the original version came out, enhanced versions with even greater control and sensitivity have become available.

Although the prototypes I used were cream-colored, in its final production form, the TrackPoint consists of a small, red, silicone rubber knob nestled between the G, H, and B keys on the keyboard. The primary and secondary mouse buttons are placed below the spacebar where you can easily reach them with your thumbs without taking your hands off the keyboard. Newer versions also include a third button which can be used for scrolling.

Studies conducted by Selker found that the act of removing your hand from the keyboard (to reach for a mouse) and then replacing your hand back on the keyboard takes approximately 1.75 seconds. If you type at 60 wpm (words per minute), that can equal nearly two lost words every minute, not including the time lost while you regain your train of thought. Almost all of this time can be saved if you use the TrackPoint to move the pointer or make a selection (click or double-click) instead of a mouse. The TrackPoint also enables you to perform drag-and-drop functions easily.

IBM’s research also found that people can get up to 20% more work accomplished using the TrackPoint instead of a mouse, especially when the application involves a mix of typing and pointing activities, such as with word processing, spreadsheets, and other typical office applications. In usability tests with the TrackPoint, IBM gave a group of desktop computer users both a TrackPoint and a traditional mouse. After two weeks, 80% of the users had unplugged their mice and switched solely to the TrackPoint device. Selker is convinced (as am I) that the TrackPoint is the best pointing solution for both laptop and desktop systems.

Another feature of the TrackPoint is that a standard mouse can be connected to the system at the same time to enable dual-pointer use. This setup not only enables a single person to use both devices, but also enables two people to use the TrackPoint and the mouse simultaneously to move the pointer on the screen. The first pointing device that moves (thus issuing a system interrupt) takes precedence and retains control over the mouse pointer on the screen until it completes its movement action. The second pointing device is automatically locked out until the primary device is stationary. This enables the use of both devices and yet prevents each one from interfering with the other.

IBM/Lenovo has added various versions of the TrackPoint to its laptop computers, as well as to high-end keyboards sold under the IBM/Lenovo, Lexmark, and Unicomp names. Laptop computer makers, such as HP/Compaq, Dell, and Toshiba, have licensed the TrackPoint device (Toshiba calls it Accupoint) and use it on various models.

I have compared the TrackPoint device to other pointing devices for laptops (especially touch pads), but nothing compares in terms of accuracy and control—and, of course, the fact that you don’t have to take your hands off the keyboard to use it!

Unfortunately, most of the TrackPoint devices used by laptops other than IBM/Lenovo don’t have the full features of the IBM/Lenovo versions, especially including the multiple tip choices, the third scroll button, and “negative inertia” control. One important feature to look for is the ability to accept different IBM/Lenovo TrackPoint caps. These have a square hole in them and allow choosing from several different types.

Over the years IBM/Lenovo has upgraded the TrackPoint pointing stick to the TrackPoint III and the current TrackPoint IV. Two main differences exist in the III/IV system, but the most obvious one is the rubber cap. The original caps were made from pure silicone rubber, which was grippy and worked well in most situations. However, if the user has greasy fingers, the textured surface of the rubber can become slippery. Cleaning the cap (and the user’s hands) solves the problem, but it can be annoying at times. The TrackPoint III and later standard caps are made from a different type of rubber, which Selker calls “plastic sandpaper.” This type of cap is much more grippy and does not require cleaning except for cosmetic purposes. More recently IBM/Lenovo introduced other caps that do not feature the sandpaper surface, but have either a wider soft dome or a wider concave surface for additional grip. IBM/Lenovo now has three different types of caps for the TrackPoint to suit different needs and tastes. These different caps are interchangeable with the older styles as well (see Figure 15.14):

• Classic dome (P/N 84G6537)—The traditional “pencil eraser” cap with a sandpaper surface.

• Soft rim (P/N 91P8423)—A larger concave non-sandpaper design creates a mechanical advantage, requiring less force for pointer motion.

• Soft dome (P/N 91P8422)—A larger convex design with a soft texture non-sandpaper surface.

Figure 15.14 Classic, soft rim, and soft dome TrackPoint caps.

The other difference between the IBM/Lenovo TrackPoint and some of the others on the market is the control software. IBM/Lenovo added routines that implement a subtle technique Selker calls “negative inertia,” which is marketed under the label QuickStop response. This software not only takes into account how far you push the pointer in any direction, but also how quickly you push or release it. Selker found that the improved software and caps enable people to make selections up to 8% faster.

The latest incarnation (called TrackPoint IV) includes an extra scroll button, as well as the ability to press the TrackPoint cap to select as if using the left mouse button. These new features make the TrackPoint even better.

The bottom line is that anyone who touch types should strongly consider only laptops that include a TrackPoint device. TrackPoints are far superior to other pointing devices such as touch pads, because the TrackPoint is faster to use (you don’t have to take your hands off the keyboard’s home row), easier to adapt to (especially for speedy touch typists), and far more precise to control. It takes some getting accustomed to, but the benefits are worth it. I know many people who have converted from using touch pads to TrackPoints, but few who have willingly gone the other way.

Note that the benefits of the TrackPoint are not limited to portable systems; you can have the same features on your desktop keyboard. For desktop systems, I use an IBM/Lenovo keyboard with the TrackPoint built in. This makes for a more consistent interface between desktop and laptop systems because I can use the same pointing device in both environments. You can buy these keyboards directly from IBM/Lenovo or www.clickykeyboard.com.

Alternative Pointing Devices

Because of Windows, many users spend at least as much time moving pointers around the screen as they do in typing, making pointing device choices very important. In addition to the mouse and the pointing stick choices discussed earlier in this chapter, several other popular pointing devices are available:

• Touch pads

• Trackballs

• Ergonomic (upright) mice

All these devices are treated as mice by the operating system but offer radically different options for the user in terms of comfort. If you’re not satisfied with a regular mouse and don’t want to use an integrated pointing stick such as the TrackPoint II/III/IV, look into these options.

Touch Pads

The first touch pad was included on the ill-fated Gavilan portable computer in 1982; however, it didn’t catch on until many years later. Cirque originated the modern touch pad (also called a track pad) pointing device in 1994. Cirque refers to its technology as the GlidePoint and has licensed the technology to other vendors such as Alps Electric, which also uses the term GlidePoint for its touch pads. The GlidePoint uses a flat, square pad that senses finger position through body capacitance. This is similar to the capacitance-sensitive elevator button controls you sometimes encounter in office buildings or hotels.

When it is used on a portable computer’s keyboard, the touch pad is mounted below the spacebar, and it detects pressure applied by your thumbs or fingers. Transducers under the pad convert finger movement into pointer movement. Several laptop manufacturers have licensed this technology from Cirque and have incorporated it into their portable systems. Touch pads are also integrated into a number of mid-range to high-end keyboards from many vendors. When used on a desktop keyboard, touch pads are often offset to the right side of the keyboard’s typing area.

Touch pads feature mouse buttons, although the user also can tap or double-tap on the touch pad’s surface to activate an onscreen button located under the touch pad’s cursor. Dragging and dropping is accomplished without touching the touch pad’s buttons; just move the cursor to the object to be dragged, press down on the pad, hold while moving the cursor to the drop point, and raise the finger to drop the object. Some recent models also feature additional hot buttons with functions similar to those on hot-button keyboards, as well a vertical scrollbar on the side and the capability to tap the touch pad to simulate a mouse click.

The primary use for touch pads has been for laptop computer– and desktop keyboard–integrated pointing devices, although Cirque and Alps have both sold standalone versions of the touch pad for use as a mouse alternative on desktop systems. Cirque’s touch pads are now available at retail under the Fellowes brand name, as well as direct from the Cirque website. The Internet Touchpad (also sold by Fellowes) has enhanced software to support touch gestures, has programmable hot buttons, and includes other features to make web surfing easier.

Although it has gained wide acceptance, especially on portable computers, touch pad technology can have many drawbacks for some users. Operation of the device can be erratic, depending on skin resistance and moisture content. The biggest drawback is that to operate the touch pad, users must remove their hands from the home row on the keyboard, which dramatically slows their progress. In addition, the operation of the touch pad can be imprecise, depending on how pointy your finger or thumb is! On the other hand, if you’re not a touch typist, removing your hands from the keyboard to operate the touch pad might be easier than using a TrackPoint. Even with their drawbacks, touch pad pointing devices are still vastly preferable to using a trackball or a cumbersome external mouse with portable systems.

Unless you want to use a “real” mouse with a portable system, I recommend you sit down with portable computers that have both touch pad and TrackPoint pointing devices. Try them yourself for typing, file management, and simple graphics and see which type of integrated pointing device you prefer. I know what I like, but you might have different tastes.

Trackballs

The first trackball I ever saw outside of an arcade was the Wico trackball, a perfect match for mid-1980s video games and computer games, such as Missile Command and others. It emulated the eight-position Atari 2600 analog joystick but was capable of much more flexibility.

Unlike the mid-80s trackballs, today’s trackballs are used primarily for business instead of gaming. Most trackballs use a mouse-style positioning mechanism—the differences being that the trackball is on the top or side of the case and is much larger than a mouse ball. The user moves the trackball rather than the input device case, but rollers or wheels inside most models translate the trackball’s motion and move a cursor onscreen the same way that mouse rollers or wheels convert the mouse ball’s motion into cursor movement.

Trackballs come in a variety of forms, including ergonomic models shaped to fit the (right) hand, ambidextrous models suitable for both lefties and right-handers, optical models that use the same optical sensors found in the latest mice in place of wheels and rollers, and multibutton monsters that look as if they’re the result of an encounter with a remote control.

Because they are larger than mice, trackballs lend themselves well to the extra electronics and battery power needed for wireless use. Logitech offers several wireless trackball models that use radio-frequency transceivers; for details of how this technology works, see the section “Wireless Input Devices,” later in this chapter.

Trackballs use the same drivers and connectors as conventional mice. For basic operations, the operating system–supplied drivers will work, but you should use the latest version of the vendor-supplied drivers to achieve maximum performance with recent models.

Trackball troubleshooting is similar to mouse troubleshooting. For issues other than cleaning the trackball, see the section “Mouse Troubleshooting,” earlier in this chapter.

Because trackballs are moved by the user’s hand rather than by rolling against a tabletop or desktop, they don’t need to be cleaned as often as mouse mechanisms do. However, occasional cleaning is recommended, especially with trackballs that use roller movement-detection mechanisms. If the trackball pointer won’t move, skips, or drags when you move the trackball, try cleaning the trackball mechanism.

Trackballs can be held into place by a retaining ring, an ejection tab, or simply by gravity. Check the vendor’s website for detailed cleaning instructions if your trackball didn’t come with such instructions. Swabs and isopropyl alcohol are typically used to clean the trackball and rollers or bearings; see the trackball’s instructions for details.

Ergonomic Mice

Many PC users who grew up using joysticks on the older video games experienced some “interface shock” when they turned in their joysticks for mice. And even long-time mouse users nursing sore arms and elbows have wondered whether the mouse was really as “ergonomic” as it is sometimes claims to be.

3M’s solution, developed late in 2000, is to keep the traditional ball-type mouse positioning mechanism but change the user interface away from the hockey puck/soap bar design used for many years to a slanted handle that resembles a joystick. 3M’s Ergonomic Mouse (originally called the Renaissance Mouse) is available in two hand sizes and attaches to either the PS/2 port or USB port (serial ports are not supported). The single button on the top of the handle is a rocker switch; push on the left side to left-click and on the right side to right-click. The front handgrip provides scrolling support when the special Ergonomic Mouse driver software is installed.

The Ergonomic Mouse enables the user to hold the pointing device with a “handshake”-style hand and arm position. 3M’s website provides detailed ergonomic information to encourage the proper use of the Ergonomic Mouse, which comes with software to support scrolling and other advanced functions. It’s available in two sizes, along with various colors and separate models for Windows-based PCs and Macs.

Wireless Input Devices

For several years, many manufacturers have offered wireless versions of mice and keyboards. In most cases, these devices have used either infrared or short-range radio transceivers to attach to standard USB or PS/2 ports, with matching transceivers located inside the mouse or keyboard. Wireless input devices are designed to be easier to use in cramped home-office environments and where a large-screen TV/monitor device is used for home entertainment and computing.

Many manufacturers, including Microsoft, Logitech, and second-tier vendors, offer bundled kits that include a wireless keyboard and mouse that share a transceiver. Because many of these keyboards and mice have the latest features, including programmable keys, multimedia and Internet-access keys, and optical sensors, these wireless combos are often the top-of-the-line products from a given vendor and are often less expensive than buying the keyboard and mouse separately.

The three major technologies used by wireless input devices are as follows:

• Infrared (IR)

• Proprietary radio frequency

• Bluetooth

All three technologies normally use a transceiver connected to the USB or PS/2 ports on the computer. Because many wireless transceivers are designed for use with a mouse and keyboard, PS/2-compatible versions have two cables—one for the mouse port and one for the keyboard port. A USB-compatible transceiver needs only one USB port to handle both devices if the system supports USB Legacy (keyboard) functions. The transceiver attached to the computer draws its power from the port.

The transceiver receives signals from the transceiver built into the mouse or keyboard. These devices require batteries to function; therefore, a common cause of wireless device failure is battery rundown. Early generations of wireless devices used unusual battery types, but most recent products use off-the-shelf alkaline AA or AAA batteries. Many models now use lithium-ion or NiMH rechargeable batteries in which the transceiver connected to the PC also doubles as a charger.

Although all three technologies rely on battery power, the similarities end there. IR devices have a relatively short range (12 ft. maximum), and a clear line-of-sight must exist between the input device and transceiver. Anything from a Mountain Dew can to a sheet of paper can block the IR signal from reaching the transceiver, assuming you’re aiming the transmitter built into your input device correctly in the first place. Some late-model IR devices have transceivers that can receive signals through a relatively wide 120° range, but this technology is much more temperamental than the others and has been abandoned by most vendors.

Because of the problems with IR devices, almost all vendors of wireless input devices now use radio waves (RF) for transmission between the device and transceiver. RF-based wireless devices have no line-of-sight problems, but most have a limited range of about 6 ft. from the transmitter.

Although RF overcomes line-of-sight issues that can cripple an IR mouse, early versions of RF products had a high potential for interference from other devices and from other devices in use in the same room because of a limited range of channels. For example, early Logitech wireless MouseMan products required the user to manually select the channel used by the transceiver and mouse. If more than six users in a small room had wireless devices, interference was practically inevitable and user error could lead to a user’s mouse movements showing up on the wrong computer screen.

Fortunately, improvements in frequency bands used and automatic tuning have enabled all users of a particular type of device to avoid interference with other electronic devices or with each other. For example, the 27MHz frequency pioneered by Logitech’s Palomar line of peripherals has become a de facto standard for most recent wireless input devices (it has also been used by Microsoft and IBM for their wireless products). Logitech allows users to enable a digital security feature that uses one of more than 4,000 unique codes to prevent accidentally activating another computer with a wireless device or signal snooping by another user. Most vendors use similar technology, but some might use a much smaller number of codes. The range of 27MHz RF devices is short—about 6 ft.—but the transmitter can be located behind the computer or under the desk without loss of signal. Many recent wireless products use FastRF technology, which provides 2.5 times the transmission rate of conventional 27MHz devices. The responsiveness of a FastRF connection is all but indistinguishable from a corded mouse or keyboard.

Finally, there’s Bluetooth. Although most wireless products use proprietary radio transceivers, Microsoft, Logitech, and some others have developed wireless mouse and keyboard products using the Bluetooth wireless standard. Bluetooth-enabled devices have an effective range of up to 30 ft. and might be compatible with other brands of devices that are also Bluetooth enabled.

For more information about Bluetooth, see Chapter 17, “Local Area Networking,” p. 865.

Having used both IR and RF types of wireless devices, I can tell you that a radio-frequency input device beats an infrared input device hands down for use at home or in a small one- or two-person office. It’s little wonder that IR-based mouse devices and keyboards are now all but impossible to find on a retail shelf. Today, there is little reason not to opt for an RF device even if you have the choice of purchasing a less-expensive IR peripheral. Because the cost of RF wireless products, including attractive keyboard and mouse combinations, varies widely, RF input devices are affordable for almost everyone. If you’re planning to use a computer to drive a big-screen TV or as a presentation unit, consider Bluetooth-enabled devices available from Microsoft, Logitech, and others because of their longer range (up to 10 meters, or 33 ft.).

Power Management Features of Wireless Input Devices

A wireless mouse is useless if its batteries fail, so several vendors of wireless products have developed sophisticated power-management features to help preserve battery life—especially with optical mice, which use power-eating LEDs to illuminate the mousing surface. For example, Logitech Cordless mice have four operating modes, as shown in Table 15.3.

Table 15.3 Logitech Cordless Mouse Optical Power Management

Wireless keyboards are activated only when you press a key or use the scroll wheel available on some models, so they tend to have longer battery lives than mice. Conventional ball-type mice also have longer battery lives than optical mice, but ball-type mice have largely been discontinued, as the convenience and accuracy of optical mice outweigh battery-life issues for most users.

Troubleshooting Wireless Input Devices

If your wireless input device does not work, check the following:

• Battery failure—The transceivers attached to the computer are powered by the computer, but the input devices themselves are battery powered. Check the battery life suggestions published by the vendor; if your unit isn’t running as long as it should, try using a better brand of battery or turning off the device if possible.

• Lost synchronization between device and transceiver—Both the device and the transceiver must be using the same frequency to communicate. Depending on the device, you might be able to resynchronize the device and transceiver by pressing a button, or you might need to remove the battery, reinsert the battery, and wait for several minutes to reestablish contact.

• Interference between units—Check the transmission range of the transceivers in your wireless units and visit the manufacturer’s website for details on how to reduce interference. Typically, you should use different frequencies for wireless devices on adjacent computers.

• Blocked line of sight—If you are using infrared wireless devices, check the line of sight carefully at the computer, the space between your device and the computer, and the device itself. You might be dangling a finger or two over the infrared eye and cutting off the signal—the equivalent of putting your finger over the lens on a camera.

• Serial port IRQ conflicts—If the wireless mouse is connected to a serial port and it stops working after you install another add-on card, check for conflicts using the Windows Device Manager.

• Disconnected transceiver—If you have moved the computer around, you might have disconnected the transceiver from its keyboard, PS/2 mouse, serial, or USB port. You can plug a USB device in without shutting down the system, but the other types require you to shut down the PC, reattach the cable, and restart the PC to work correctly.

• USB Legacy support not enabled—If your wireless keyboard uses a transceiver connected to the USB port and the device works in Windows, but not at a command prompt, make sure you have enabled USB Legacy support in the BIOS or use the PS/2 connector from the transceiver to connect to the PS/2 keyboard port.