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 found in a Hands-On Elctronics from 1987. The field effect transistor admits...
This VCO with the CMS 4046 was found in the August 1994 Electronics Now magazine. The frequency is...
This SCR circuit was found in an American 1980s documentation. The circuit is still current,...