This circuit converts a high voltage into a frequency using an optical coupler. The transistor can be 2N2646 and the coupler admits equivalent. The circuit is from a 1974 publication.
This circuit shows how to use the remaining gates of a 4093 or 74C14 as amplifiers. The circuit has...
Suggested by a 90s Electronic Design, this circuit drains only 0.25 mA from its source. Listening...
This circuit can be embedded in switches and sockets, thus facilitating its location in the dark....