This circuit is from an old Japanese publication of 1962. The circuit uses two batteries, one for the filaments of the tubes and the other one of high voltage for the plate circuits.
This circuit turns on an old cassette recorder when the telephone rings, thus enabling the...
This circuit was found in a Poptronics of the 90's. The circuit limits the load current to 0.6 A....
Incandescent lamps and heaters can be controlled by a low power switch using this circuit. The...