Found in an Electronics World of 1966, this circuit makes use of FETs of the time. Modern equivalents can be used. The high voltage supply suggests its use with tube amplifiers.
We found this circuit in an English documentation from 1995. With it it is possible to measure a...
This circuit is from an ancient American documentation. The coil is frequency dependent and the...
We have here a simple signaling circuit for two common incandescent lamps, which is used for...