Found in a 1966 American publication, this circuit generates a 25 MHz rectangular signal for testing flip-flops. Transistors are from the era. No information is given about L1.
I found this circuit in an old Argentine publication from 1973. The components are no longer...
This circuit has an LED indication of the timing progress, having been found in an old...
This simple signal tracer was found in a Popular Electronics from the 90's. The transistor can be a...