This circuit provides a 5 V negative voltage from a positive input voltage. Found in old American documentation, information on the used integrated circuit was not provided. Probably an oscillator.
This contact or reed switch actuation was found in a 1964 Electronic Design. The circuit can be...
This is the previous version, but with a simplification given by the use of the 7404 and 7408...
In the figure we present a circuit of a microphone signal conditioner using the SSM2167 integrated...