Using a single ultrabright l.e.d., this simple low-cost, high security, optical voice link achieved a range of four metres, and 15 metres with a single lens(not included in the kit) This project slices up the human voice into forty-thousand binary segments a second, transmits it over a light-beam, then re-integrates it at the other side.
That is, it applies pulse width modulation (p.w.m.) to the voice, to create a binary transmission. This is far more advantageous than similar analogue circuits, which typically achieve a range of no more than a few metres. The circuit presented here has a range approximately five times greater than similar analogue circuitW ithout the use of lenses, the prototype Photic Phone achieved a range of four metres. With a single lens at the Transmitter, it achieved a range of 15 metres.
That is, it applies pulse width modulation (p.w.m.) to the voice, to create a binary transmission. This is far more advantageous than similar analogue circuits, which typically achieve a range of no more than a few metres. The circuit presented here has a range approximately five times greater than similar analogue circuitW ithout the use of lenses, the prototype Photic Phone achieved a range of four metres. With a single lens at the Transmitter, it achieved a range of 15 metres.
In theory, therefore, with the use of two lenses, it should achieve a range of fifty metres using a single cheap, ultrabright l.e.d. The problem with similar analogue circuits is that these depend on a light beam of continuously variable intensity. What happens in this case is that, over distance, the subtler nuances of the light beam are lost – and with them the intelligibility of the voice.
Transmitting a voice in binary form has the advantage of always transmitting at full intensity. This means that even the weakest nuances of a voice will reach the Receiver as strongly as the rest. Lighting The Way Besides being good fun, communicating via a light-beam may have certain advantages over other methods of transmission. It requires no wires, it needs no radio license, it is very cheap to implement, and it is all but impossible for anyone to eavesdrop on a transmission. Not only this, but the PROJECT may also be used with fibre optic cable or a laser (at a price)s.
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