IR remote control

(InfraRed remote control) A handheld, wireless device used to operate audio, video and other electronic equipment within a room using light signals in the infrared (IR) range. Infrared light requires line of sight to its destination. Low-end remotes use only one transmitter at the end of the unit and have to be aimed directly at the equipment. High-quality remotes have three or four powerful IR transmitters set at different angles to shower the room with signals.

All Functions Are Coded
Using very low data rates, typically no more than 1,000 bits/sec, infrared remotes send a different code for each function on the TV, DVD, A/V receiver, etc. There are hundreds of remote control codes for A/V devices manufactured over the years. A programmable remote may be customized by selecting built-in code sets, by downloading code sets from the Internet or by training the remote to accept signals from another handheld remote.

IR Receivers for Closed Cabinets
In home theater applications, IR receivers are commonly used to control components in a cabinet with closed doors that obstruct the line of sight required by infrared. An IR sensor is located near the TV and wired to the receiver, which can be many feet away in the equipment rack. The receiver has an amplifier and an "IR blaster" that showers IR signals to all components by reflecting off the closed cabinet doors. The receiver also has sockets for several IR emitters (IR flashers) that are wired to, and pasted directly over, the IR sensors for precise aiming.

RF to IR
High-end, third-party remote controls use radio frequencies (RF) instead of infrared. Such remotes neither have to be aimed, nor even be in the same room, but they require a base station that accepts the RF and converts it to IR (see RF remote control). See Wi-Fi remote control.

High-End IR Remote

The MX-850 from Universal Remote Control (www.universalremote.com) transmits IR and RF simultaneously. High-end remotes such as this use multiple IR transmitters for broad coverage. Programmed via the PC to make complex tasks easy, the green "M" keys have been assigned macros to power multiple units. The functions on the blue "L" keys were learned by beaming IR signals from the original remotes into the MX-850. See RF remote control.

An IR Emitter

An IR emitter (left) is pasted onto the IR sensor on this DVD/VHS player. The wire traces back to a Home Theater Master RF base station that picks up radio signals from the remote and converts them to infrared. No matter whether the remote control is IR or RF, the signal generally winds up as IR at the equipment.

The First "Light Beaming" Remote

In 1955, Zenith's Flash-Matic beamed light rays to sensors at the corners of the TV screen to change channels and mute the sound. Because it did not use infrared, changing light conditions in the room sometimes triggered the unit. (Image courtesy of Zenith Electronics LLC.)