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 source of constant current was obtained in an American documentation of 1973. The transistors can be...
When light fails to focus on the sensor, a common photo-transistor, the relay closes its contacts....
This low impedance circuit was found in an Electronic Design from the 90's. Operational amplifiers admit...