This signal injector and tracer (follower) was found in an old American documentation. The transistors can be general use and power is made with one or two common cells.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...