This circuit is from an American 80's documentation. The circuit indicates when the voltage of a 9 V battery drops below 7 V. The transistors can be BC548.
This circuit was found in a 1958’s publication. It uses germanium transistor, availble that time....
This low-current power supply was obtained in Japanese documentation from 1968. The currents are...
I found this circuit in an Electronics Handbook, an American publication from 1989 and that no...