When the power is cut off, this circuit keeps the flashlight on for a while, allowing it to be located. The circuit is from a Radio Electronics from September 1992.
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
This traditional crystal radio circuit, but which has a modern version with diode, was found in an...
This headphone amplifier using a pickup coil can be used as an extension for devices such as TVs,...