Remote control

The remote control lets you run the TV from across the room. Press a button and it sends a short code, as flashes of invisible infrared light, that the TV's infrared receiver decodes.

Its case is two shells of ABS plastic, injection molded and snapped or screwed together. The buttons are a single molded sheet of silicone rubber. Under each key is a small pill of silicone filled with carbon black, which makes it conduct. Beneath lies a printed circuit board with a pair of interlocking copper tracks under every key. Press a key and its carbon pill bridges the tracks, closing a circuit. A microcontroller, a small integrated circuit, notices which key closed and flashes an infrared LED at the front in that key's pattern. Two alkaline batteries, held between steel springs and contacts, power it. Because the chip sleeps between presses, they can last a year or more.

Early TV remotes of the 1950s used a wire, visible light or ultrasonic sound. Infrared took over around 1980. Many newer remotes also use Bluetooth or radio, so they work without pointing and can take voice commands.