Heterodyne Mixer (CB4291E)

This is a typical 80's FM radio mixer circuit. The circuit was found in a documentation of the time.

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Rain Alarm or Door Bell (CB5369E)
This circuit was found in a 1980s documentation. Q1 and Q2 can be BC548 and SCR a TIC106. The...
Smoke detection ionization chamber (CB4887E)
This circuit is from an 80's publication. The basic components indicated are of the time, mainly...
Audible Thermometer (CB5017E)
This interesting multivibrator was found in an Italian magazine that no longer exists. This is...