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 circuit is a high voltage source for a gas LASER. We found it in a documentation from the...
This intercom with wires up to 30 meters separation between the stations is from the Linear...
This circuit is from an old American publication from 1977. Transistor Q1 can be a TIP42 and Q2 a...