What is Remote Control and how does it work ?

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?

when you aim your remote at a neighbor's house, does their TV channel change too? Let's take a closer look at the mysteries of remote control!

The first thing you notice about a remote control unit is that it has no wires, so it has to send signals to whatever it's operating 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 infrared radiation (which is a kind of invisible red light that hot objects give off and halogen hobs use to cook with), though some use radio waves instead.

If you look at the top of your remote control unit, you'll see there's a small plastic light-emitting diode (LED) where the infrared radiation comes out. Now take a look at your TV or video.

Somewhere on the front, 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.

Human eyes can't detect infrared, so even if you press the buttons on your remote and stare at the LED you won't see anything happening.

Some animals, including rattlesnakes, can detect infrared. Rattlesnakes have tiny infrared detectors buried in pits near their eyes, which work a bit like the infrared detectors on your TV. By homing in on infrared heat, snakes can locate prey at night when there's no ordinary light to see by.

What would happen if you pointed a TV remote control at a snake and pressed the buttons? Maybe it would think you were a mouse and slither over to eat you. It's unlikely you could control a rattlesnake with a TV remote—and we don't recommend you try!

It's no good the remote control just sending out a burst of random infrared. Clearly if your remote control has 20 or more buttons on it,

Before you dismiss these stories as nothing more than old wives' tales, take a moment to consider that life a few decades ago might indeed have been more difficult than it is today

it must have a way of sending out at least this many signals—each one different enough for your TV to be able to decode and understand it.

Instead, they had to do research with real books! Can you imagine? If that amazes you, you'll be really surprised by how different it was to watch television. In addition to having only a dozen channels rather than hundreds, they also had to walk across the room to turn a knob on the television set if they wanted to change channels!

When you press one of the buttons, the remote generates a systematic series of on/off infrared pulses that signal a binary code (a way of representing any kind of information using only zeros and ones, which computers use).

So a short pulse of infrared could signal a 1 and no pulse could signal a 0. Sending many infrared pulses, one after another, allows your remote to send whole strings of zeros and ones. One code (maybe it's 101101) might mean "volume up", while another (perhaps 11110111) could mean "mute sound."

As well as sending out pulses that tell the TV what you want it to do, the remote also sends a short code that identifies the product you're trying to control (for example, 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.

Generally, this means each remote control unit can operate only one appliance made by only one manufacturer. Of course if you could discover the codes that different TVs and videos understand, you could build a remote control that operated any appliance. This is how universal remotes work.

They let you control any TV or video and, instead of sending out only signals specific to one brand of equipment, they can send out codes that any make or model can understand.

One inventor has even gone so far as to develop a remote called TV-B-Gone that systematically sends out a "switch TV off" signal using every possible manufacturer's code.

It's designed to allow TV haters to switch off annoying TVs covertly as they wander through shopping malls and department stores!

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 neighbor's TV or DVD recorder by accident!

If you do want to operate equipment in other rooms, it's possible to buy radio-frequency remote controls (and adapters for conventional, infrared remotes) to extend their range.