Telephone Busy Indicator (CB24430E)

This circuit for analog telephones from the 90s was found in documentation from the time. It lights up a remote LED when the extension is in use.

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Audio Compressor For Guitar (CB10488E)
I got this circuit from an English magazine from 1977. It can still be easily assembled, as the...
Two Phase Motor Driver (CB5419E)
This two-phase stepper motor circuit was found in an old documentation using an operational amplifier...
Pulse Generator 741 (CB19109E)
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