I remember my kiddy days when my friends and I used to play with toy telephones made up of a couple of small match box containers with strings tied in between them as a link. When tightly stretched one could speak, or rather whisper, close over one of the containers and the voice vibrations would get carried through the string up to the person at the receiving end where it could be heard slightly amplified over the respective container… primitive, though, but interesting.
Children always love making and playing with stuff that is easy and quickly done. Simple projects like the above will always retain their attraction especially with the kids, no matter how much the technology advances.
Another similar type of toy telephone (though comparatively a little advanced) is discussed in this article. Unlike the above concept which uses mechanical vibrations to transfer sound waves, the present design utilizes electrical signals for the purpose (without using external electricity). It’s ideally a kid’s project and they will surely love making and playing with it.
Although the present design is just a toy, that doesn’t stop it from being technical and involving quite a bit of understanding.
The idea is based on the fact that electrical vibrations are converted into sound vibrations over loud-speakers. We all know that, however, the results can also be inverted through these devices, i.e. anything spoken very close to the diaphragm of a speaker may well get transformed into minute electrical pulses. These converted electrical pulses, though quite weak, if fed into a speaker back again will get transformed to sound vibrations over its diaphragm.
Let’s see how we can build this toy telephone and also understand its functioning.