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.
The circuits below were found in amarican publication of the year 1958. The transistors are...
This circuit produces signals that depend on the input control voltage. It is a Voltage Controlled...
The bipolar transistors may be BD136 and BD136 and FET of any type for 1 A current at least. The...