Found in a 1992 book, this circuit is intended for operation with audio signals. Equivalent operational amplifiers can be used. The optical coupler is an unusual type today.
This circuit is from a technical documentation from the 70s. It makes use of married transistors in a...
This strobe light circuit with incandescent lamp was found in a 1978 publication. We can mount it with...
This circuit produces a square wave signal with the frequency determinated by R1 and C1. The upper limit...