How can you change TV channels at the speed of light?

Man with a tv remote control sitting in a living room

Remote controls are a perfect indulgence for couch potatoes everywhere—but have you ever stopped to wonder how they work? How come your TV remote doesn’t trigger the video? Why do you have to point it directly at the TV? And when you aim your remote at a neighbour’s house, does their TV channel change too? Remote control has no wires, so it has to send signals to the device using electromagnetic waves.

Light, x-rays, radio waves, and microwaves are all examples of electromagnetic waves – vibrating packets of electrical and magnetic
energy that travel through the air at the speed of light. Most remote controls send signals using infraredradiation.

There is a small plastic light emitting diode (LED) at the top of remote control unit where the infrared radiation comes out.

Somewhere on the front of your TV or video, there’s a very small infrared light detector. When you press the remote control, a beam of infrared radiation travels from the remote to your TV at the speed of light and the detector picks it up.

When you press one of the buttons, the remote generates a systematic
series of on/off infrared pulses that signal a binary code. One code (maybe it’s 101101) might mean “volume up”, while another (perhaps 11110111) could mean “mute sound.”

The remote also only sends a short code to a specific make and model of TV. That ensures your remote operates only the TV, not the video, and not any other TVs that happen to be nearby.

Infrared remote controls are relatively low powered and will send signals only about 10–20m (35–70ft). Like visible light, infrared is relatively low-energy electromagnetic radiation and, unlike radio waves, cannot penetrate through solid walls.

That means there’s no chance your ordinary infrared remote will switch on your neighbour’s TV or DVD recorder by accident!