a 555 timer IC, such as RadioShack part #216-1718 (There are lots of 8-pin DIP 555 timer ICs out there, and they are all basically the same.)

an 8-pin IC socket

two red or orange LEDs

a photoresistor, such as RadioShack part #276-1657 (also called a light dependent resistor, photoconductor, or CdS—cadmium sulfide—cell)

a 22k ohm resistor (coded with red-red-orange stripes)

two 470 ohm resistors (coded with yellow-purple-brown stripes)

a 120k ohm resistor (coded with brown-red-yellow stripes)

a 1.5 μF electrolytic capacitor

a 100k ohm variable resistor, preferably a linear taper

a control knob cover, such as RadioShack part #274-415

two 1/4″ mono phone jacks (guitar jacks)

a printed circuit board (Any PCB, like RadioShack #276-148, will do, but #276-159 is especially handy here; it’s the one shown in Figure 15-7.)

a small, sturdy box to serve as the project enclosure (See On Enclosures in Supplies.)

a 9-volt battery clip

a 9-volt battery

22- or 24-gauge bare bus wire

24-gauge insulated hook-up wire

a DPDT switch, such as RadioShack part #275-666

a small SPST switch, such as RadioShack part #275-612

duct tape