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.
This simple NiCad battery charger was found in an English documentation. Resistors R2 and R3...
This was a very popular instrument in the workshops of the 60s and 70s. It was a "top of the line"...
We found this circuit in a 1981 publication, when it was still possible to find 22.5 V batteries (used...