When the 24 V battery voltage drops below 18 V, this circuit cuts off its discharge. The circuit is from 1968 documentation. It can be adapted to operate with other voltages.
This circuit of a 1978 American publication monitors a telephone line by triggering a relay. The...
This interesting FET-tester circuit was obtained from an old American documentation. The bipolar...
This old VHF TV booster that also serves FM was found in Radio Electronics magazine from April...