Don't toss that old, broken radio in the trash just because the volume knob stopped working or fell off. Simply replace the potentiometer knob with a new one. A potentiometer, or pot, consists of three lugs numbered 1, 2, and 3, and a plastic or metallic stick called the shaft. The shaft turns the potentiometer to increase or decrease the value of resistance, which controls how much current is flowing in the circuit. Reliable sellers on eBay offer potentiometer kits, which include pots of various resistances. Resistance values include 100, 1K, 100K, 50K, and 500K, to name a few. Pots are available with either analog or digital input signals. Common applications for pots include volume controls on audio equipment, light dimmer switches, and contrast controls on televisions. Early patents for this type of device include Thomas Edison's "coiled resistance wire rheostat" and Mary Hallock-Greenewalt's nonlinear rheostat for her Sarabet, a visual-music instrument. History shows how useful these pieces are, so get your device back in action with new or used a replacement pot.