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 a publication from the 1970s. It produces intermittent clicks on a...
We found this circuit in the 1994 National Semiconductor Linear Applications Handbook. The circuit is...
This circuit is from 1977 Radio Shack documentation. The circuit modulates an LED (which can be...