Suggested by a Popular Electronics from the 90s, this circuit triggers an external load, relay or recorder, when the telephone line receives a call, thus enabling its recording.
This circuit was obtained in an American publication from the 1980s. The circuit uses a transistor at...
This gas sensor circuit was found in July 1976 Radio Electronics magazine. The TGS sensor was a...
This assembly is from 1957 from a Raytheon manual, but can be modernized using a BC548, 6 V power...