This circuit was found in an American publication from 1968. The transistors are from the time, but it can be made from modern transistors.
It is like to the previous circuit with a lock that keeps the LED on at the end of the timer. The...
This circuit was obtained in a 1972 RCA power transistors manual. The transistor admits...
No information is given about the transformers in this circuit suggested by Motorola in a 1968...