We found this circuit in an English publication from the 60's. The transistors are of germanium of the time and the headphones must be high impedance magnetic.
This photometer is based on a Wheatstone bridge that must be balanced by the linear potentiometer P1. The...
This 1997 documentation circuit was originally created for use with Camcorder type video cameras....
This simple circuit tests both monophonic and other two-wire audio cables. The circuit is powered...