Wattmeter (T1351E)

This circuit is from a February 1949 Radio Electronics magazine. The circuit uses 3 tubes and includes the power supply.

Multivibrator with relay (CB24638E)
In the figure we have two possible configurations for multivibrators with relay. The idea comes...
Analog Isolator (CB13571E)
This circuit serves to isolate analog signals, for example, audio signals in a secure link...
Synchronizer (CB22212E)
We found this circuit in an old English documentation. Its purpose is to synchronize circuits. The...