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 an English publication from 1989. The integrated circuit is an...
This circuit was obtained from a 1964 magazine and has some interesting features such as the input...
Using a general-purpose transistor this AC amplifier was found in the November 1993 issue of...