This circuit was found in a 1945 publication. The circuit was stated to be part of a walk talkie. Note that, as it is a portable assembly, it was powered by batteries. The jack was for microphone insertion.
This circuit using only transistors was obtained from Ferranti's 1969 documentation. It can be...
This sensitive circuit can be designed with FETs such as BF245 and MPF102. The sensor is a silicon...
Found in Popular Electronics from the 90s, this circuit generates two tones that are selected by a...