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 circuit was found in an American documentation from the 80's. The components are from that...
The circuit shown is from the Texas Instruments optoelectronics manual. It is intended for audio...
This circuit drive an LED with constant current determined by the values of the resistors of 10...