The transistor in this project found in the July 1994 issue of Electronics Now magazine can be any general-purpose type. The circuit is powered by the relay voltage up to 12 V.
This simple circuit uses small speakers for both listening and speaking (microphone). The feeding is...
This old circuit for circuit breaker cars was found in a 1963 publication. The transistors are...
This is the receiver circuit for the previous transmitter (CB19628E). The receiver is an infrared...