Suitable for clandestine listening and in SMD assembly, this circuit was found in the Radio Eletronics magazine of August 1988. The listening is in headphones and the amplifier is electret.
This photo-relay uses a Darlington stage to increase sensivity. Any photo-transistor can be used....
The purpose of this circuit found in an American 1980s documentation is to produce a current pulse to...
This circuit, which can be used as a shield, was found in American documentation from the 1970s....