This circuit, found in a 1964 US documentation, consists of a selective amplifier that lets only 10 Hz pass around a 400 Hz center frequency with the indicated components.
This simple circuit causes an LED to light up when the battery voltage drops below the voltage set in the...
Obtained from a 1967 documentation, this circuit uses transistors from the time. The galvanometer can be a...
The figure shows how to implement an alarm buzzer in an LM3914 to warn about crossing the scale...