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 version of a mixer with a transistor appears elsewhere in this section and on this website. The...
This circuit, from a 1995 publication, powers incandescent lamps according to the power grid. The...
This circuit is intended for underwater communications. Of course, the critical point is the...