Found in American documentation from the 1980s, this circuit prolongs the ringing of a doorbell or chime powered by a 6 V continuous voltage. The transistor can be a BD136.
This interesting circuit was found in a 1967 Japanese documentation. Transistors are types of...
This assembly circuit using a small motor as a generator was found in Radio Electroics magazine from...
This circuit is of great use today, when solar energy is becoming increasingly important. The...