Dual function timer (CB20363E)

This circuit was found in 80's telecom documentation. Its purpose is to control a microphone in the process of transmitting voice and Morse signals.

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Blocking oscillator (CB6921E)
This blocking oscillator configuration was found in a 1964 American book. The circuit can be...
Tunnel Diode Listening Transmitter II (CB19426E)
This low power circuit for the FM band was found in a spy book from the 90s. The tunnel diode is...
FM AC Transmitter (CB20347E)
This transmitter, indicated for espionage applications, is permanently powered by the power grid....