Remote controller are small electronic device used to control another device. Infrared signals and radio frequency signals are in use. They allow operation of devices that are out of convenient reach for direct operation of controls. They function best when used from a short distance. This is primarily a convenience feature for the user.  They adjust various settings such as television channel, track number, and volume.  Modern controls feature more control functions.

Infrared signals control most electronic equipment. Infrared diode emits invisible beam of light.

Multichannel remote controls use sophisticated technology to modulate carrier signals, demodulate received signals, and split signals for distinct remote control tasks using a variety of frequency filters. These infrared signals are in direct line of sight. They reflect a mirrors just like any other light source.