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 1980 documentation. The triac used is of the TIC226D type which in the...
This circuit was obtained in a General Electric documentation from the 80's, and can be used as a...
Found in a 1967 Ferranti documentation, this regulator makes use of an operational amplifier of the...