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 from Radio Electronics from the 90s. The infrared sensor is of an...
This circuit is from the 1993 Motorola Linear Interface ICs. The circuit must use symmetrical power...
This circuit was found in the magazine of radio amateurs 73 in a 90's edition. The components are...