What is Remote Control and how does it work ?

A typical RF remote might operate in the frequency range 400–450 MHz, where an ordinary infrared remote would operate at perhaps 300 THz (3 × 1014 Hz = 300 million million hertz)—roughly a million times higher frequency.

equipment like this, it is possible to receive signals from a neighbor's home, much like you can receive their wireless Internet (Wi-Fi) signals.

US electrical engineer Eugene Polley (1915–2012) came up with the idea for an electronic remote control system years before many people even owned a television.

here it is, as drawn by the inventor himself! What we have to remember is that mid-20th-century televisions were nothing like as sophisticated as modern ones.

Although they were essentially electronic, they still had mechanical tuning systems (so you turned a clunky dial to make the tuner switch from one receiving frequency to another, much like you still do with analog radio sets to this day). That meant Polley's remote control was a part electronic, part mechanical device, and quite a bit more cumbersome than the ones we have now, although no less ingenious.

With no moving parts, you might think a remote control would last forever.

all that pushing and poking eventually takes its toll. One day, you may find your remote stops working: the buttons you press no longer do anything, no matter how hard you prod them.

This can be a real nuisance, because chances are your TV is now obsolete and the remote you need is no longer manufactured. Fortunately, it's often possible to repair a defunct remote. If the entire remote stops working, most likely the batteries have gone. That's the first, most obvious thing to test before you go any further.

If only a couple of buttons have gone—typically the volume up/down or channel buttons, or other buttons you use most often—you have a different problem.

Remotes are built around a rubber membrane keypad.

Each key is part of a single, large piece of rubbery plastic. Under each one, there's a thin strip of conducting paint or plastic. When you press the key down, the conducting material bridges contacts on the printed circuit board directly underneath, completing a switch and activating the circuit.

In the top photo here, you can see the membrane keypad (second from the right) and the circuit board it sits on (second from the left). Over time, a thin greasy film builds up between the bottom of the keys and the top of the circuit board.

I'm not sure what causes this, and it doesn't really matter (probably as the current flows through the conducting material on the base of the key it warms up slightly and that gradually degrades the material).

This film acts as a barrier between the base of the key and the circuit board and stops the keys from completing the circuit.

How to fix it? First, remove the batteries. Next, carefully open the case of your remote. You'll either have to undo some screws or, with a remote like the one shown here, separate the top of the case from the bottom with a thin, flat screwdriver.

Generally, if there are no screws, there are several plastic clips holding the two parts together and you need to find them and push them gently to open the case.

Go carefully! Once you've taken the case apart, separate out the layers as I've done here.

Inspect the circuit board, particularly the bits of the board that are directly underneath the buttons that aren't working.

See a film there or a dirty deposit? Put a small amount of detergent and water on a cloth and carefully wipe it away.

Don't use anything abrasive. Gently wipe the bottom of the rubber membrane keys to remove any film from there too.

Do this very carefully so you don't damage or degrade the conducting layer.

Make sure the whole thing is completely dry, reassemble it, and you may well find it works again.

If it still doesn't work, the conducting layer on the base of the non-functioning keys has probably worn away.

(If you have a multimeter, you can test the bottom of the keys to see if any current flows, and establish that this is the fault beyond doubt.)

You can buy repair kits and conducting paint pens to touch up the damaged layers, but they're quite expensive and it might not be worth the bother.