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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Stabilized Power Supply from 0 to 24 V x 1 A (CB12898E)
This power supply, found in an Argentine publication from the 1970s, uses a wire potentiometer of 25 W or more...
8 Channel Encoder with 4017 (CB4530E)
This circuit was obtained from an English magazine from 1979, but can be easily assembled today...
1 kHz oscillator 4001 (CB15444E)
The oscillator shown in the figure generates a 1 kHz tone that is reproduced on the speaker with...