This circuit was found in an Electronics World of 1968. The transistor can be any general purpose and the double T must be set to R3 for the desired effect.
We found this circuit in a documentation from the 50's. The transistors are germanium types. The...
Suggested by a 1966 publication, this circuit applies a 60 Hz signal to a transistor to test its...
This circuit triggers a warning LED when the standing waves reach a high value. The circuit was...