A basic Imfra Red Link for audio communication for distances upto 3 metres. Transistors can be replaced with 2N3904 and 2N2222. In his circuit Milan has created a basic Infra Red transmitter and receiver. The transmitter comprises a single amplifying stage driving two series connected IR LEDS.
The input source is connected to J1. Please note that the device will pass a small DC current through it and also directly bias the transistor. A suitable device is therefore a high output crystal microphone. These can produce high output voltages up to 1