Phone circuit (CB8709E)

With this circuit, found in a 80s Popular Electronics, it is possible to use two ordinary phones in a basic intercom.

Overvoltage and Undervoltage Relay (CB17023E)
This conventional window detector circuit was found in a 1995 documentation. The trigger points, that...
Alternator Regulator (CB26296E)
Found in a Radio Electronics store from the 90s, this circuit is for cars of that era. The circuit...
Power Output Flip Flop (CB20129E)
This old circuit excites lamps but can be modified to excite high-power LEDs or other loads...