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.
Using an operational amplifier of the time, this circuit was obtained from a 90s Radio...
This circuit, which appears elsewhere in this section, is from a 1969 Electronic Experimenter...
This circuit is one of many of its kind that can be found on this site. This one is from a...