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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Tuned active antenna (CB8412E)
Found in a 90s Popular Electronics, this circuit allows to select the operating ranges between...
Telephone amplifier (CB7502E)
This circuit was obtained in a 1960 transistor manual from Sylvania. The circuit uses small...
Unijunction Metronome (CB23525E)
This simple unijunction circuit is from a Radio Electronics from July 1963. It can be assembled with a...