Found in a September 1992 Radio Electronics magazine article, this circuit generates a pulse as shown in the graph below the diagram. The timings can be changed by swapping C3 and C7.
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,...