This circuit was obtained from 1967 documentation. It uses a sensor to determine the trigger point. The components are of the time, difficulty to obtain these days.
This circuit was found in an American 80's documentation. The transistor is of germanium of the...
This circuit produces a signal in the range corresponding the the VHH channels between 2 and 6....
Using a general-purpose transistor this AC amplifier was found in the November 1993 issue of...