How do electronic car keys work?

My mum doesn’t need a key to open the car – she does it with a funny keyring thing. How does it work?

mumbuttonLots of cars have electronic keyfobs – they look a bit like a keyring but by pressing a special button the car doors can unlock, the boot can open and sometimes you can even start the engine.

So, how do they work?  Well it’s all done with radio waves.

Radio waves are like packets of energy that can move through the air. They’re called waves because they move a little bit like the waves in the sea, with peaks and troughs.

Different radio waves have differently sized peaks and troughs, and it’s those differences that help each gadget unlock the right car.

When your mum gets near the car and presses the button, the keyfob sends a radio signal which is carrying a special set of codes.

Inside your car there is a radio receiver.  It listens out for any radio waves and it has a copy of the same set of codes. If the codes match, the doors open and, if not, nothing happens!

In the past there weren’t as many frequencies and codes in use and so your keyfob might have been able to open someone else’s car… but nowadays codes are much more complex with nearly a trillion combinations.

Many key fobs will even have an immobiliser chip inside. This carries another code for the receiver to match – and if it doesn’t, even if the doors open, the engine won’t start!

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