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.
The existence of field effect transistors at the input of the integrated circuit (operational...
This circuit generates a siren sound. It was found in the April 1969 Radio Electronics magazine. The...
Suggested by Siliconix in documentation from the 90s, this circuit can present gains of digitally...