AC Tachometer (CB9353E)

This circuit was found in a 1969 EEE. It detects when there is a phase failure in a circuit using an inductive sensor.

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Battery Low Indicator (CB4796E)
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...
Capacitive relay (CB23765E)
We found this circuit in a Radio Electronics from January 1967. The SCR is already the C106, which...
Old power supply (CB23622E)
This power source with silicon diodes at a time when valves were still used was found in Radio...