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 is from an old National Semiconductor component manual. The circuit can be...
Based on a Linear Technology integrated circuit not currently easy to obtain this circuit converts the d...
This low power metronome produces pulses in a small loudspeaker. Pule rate is adjusted by P1 and...