This circuit, which can be used as a shield, was found in General Electric documentation from the 1980s. The coupler uses a photo-SCR. The circuit admits equivalent components.
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...