That's the frequency, Kenneth

Compo answers, and some form of explanation

Last November we kicked off a competition to identify the radio frequencies used by various bits of kit around the modern home, and now we have a winner, and some explanatory notes.

No one managed a clean sheet – of the 18 questions the maximum score was 16 and only a handful of readers managed that. But from the random hat we selected Peter Woods as our winner, and will be dispatching the promised bag of goodies post haste.

We had several requests for explanations, as many of the devices weren't immediately recognisable. So there follows descriptions of the photographed items, along with the correct answers for those who care:

We started with a hard one – this cheapo remote-controlled helicopter uses IR light for control, around 340THz in frequency. Sadly it is almost impossible to control as demonstrated by the fact that since the competition this helicopter suffered a fatal collision with a light fitting.

Here we have three antenna designed for sending tiny quantities of data quite long distances at 433MHz. This is a sonar level indicator for a domestic oil tank. It bounces sound waves off the oil so the level can be displayed on an in-house receiver; slightly over the top just to avoid looking at the tank indicator, but these days it's a standard option. Sadly this too is no longer in use, the oil tank having split with some drama earlier in the year due to (apparently) too much sunlight.

Most people recognised the unlicensed 433MHz band.

Back to normality: this is a Bluetooth mouse from Microsoft, and like all things Bluetooth, for the moment at least, it uses 2.4GHz.

Still about a third of the answers were wrong – as though you suspected us of some deliberate misdirection, cynics that you are.

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