Remote Control Technology

Imagine having to get up from the couch every time you wanted to make a change to a contemporary home theater or entertainment center. The exercise might be good for some of us but all that button-pushing definitely detracts from the viewing experience. Fortunately, remote control technology makes it unnecessary. From a sitting (or napping) position, today’s users control all functions with a hand-held remote.

It wasn’t always that way: Until Robert Adler invented the first practical wireless remote control for Zenith in 1956, televisions had to be controlled manually. Adler’s device utilized sound waves to trigger simple functions such as channel changes and volume controls. By the early 1980s, sound-operated remote control technology had been replaced by infrared (IR) remotes. Capable of transmitting a wider range of information and less vulnerable to interference from outside sources, infrared light quickly became the industry standard. Light emitting diodes at the front of an IR remote produce pulses of light in the infrared range, invisible to the naked eye. The pulses of IR light carry information arranged in binary codes consisting of zeroes and ones.

Remote control technology utilized in a typical hand-held remote sends four codes in a single burst of infrared light which is repeated five times in one second. The first code is a “start” code to initialize contact with the device (TV set, DVD player, etc) the controller is actuating. The second code contains the information for the desired command — for example, a 7-digit binary code for “Volume Down.” The third code in the string is the discrete address for the specific device being controlled in order to distinguish a remote command intended for, say, the wide screen television from one intended for the cable box. A “stop” code terminates the infrared conversation with the device after the command has been performed. The pulses of IR light are received by an infrared light-sensitive photocell located on the front of the device. Internal circuitry then decodes the pulses of IR light back into binary digital information which the microprocessor in the device can utilize. After the "start" code is recognized, it reads the address code to verify that the command is intended for that specific device. Next, it reads and executes the desired command, such as “Volume Down.” The “stop” code follows, ending the command sequence. Remote control technology is not limited only to IR light transmissions.

Longer range remote control commands, or commands transmitted from adjoining rooms or areas not in line-of-sight with the device to be controlled, are often transmitted by radio (RF) waves. A prime example of RF remote technology is the ubiquitous garage door opener most people keep in their vehicle or car alarm remotes on key rings. Similar to IR remotes, RF remotes transmit a digital binary code to communicate with the device. However, the code is embedded in a radio signal instead of light. Because RF remote control signals are typically transmitted in a storm of competing radio signals from sources such as cell phones, wifi transmissions and cordless phones, they rely upon a digital address code included in the transmission to isolate the signal to one device with the matching address; i.e. the garage door opener for your house, not your neighbor’s. One thing advanced remote control technology — IR or RF — generally doesn’t do for you is tell you where the remote is when you can’t find it, however. Check between the cushions on the couch.

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Posted By
Misty Raymond
7/5/2012

This article made alot of the things I didn't know about how the technology worked, alot more clearer.

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