Phone noise canceler (CB9402E)

This circuit was found in a 1967 American documentation. The circuit uses components of the time, applying to analog lines.

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1000 second timer (CB23601E)
The existence of field effect transistors at the input of the integrated circuit (operational...
Siren Sound (CB23943E)
This circuit generates a siren sound. It was found in the April 1969 Radio Electronics magazine. The...
Selectable gain amplifier (CB7127E)
Suggested by Siliconix in documentation from the 90s, this circuit can present gains of digitally...