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.
Other operational amplifiers series, such as MC34072, MC34074, MC35071, MC35072, MC35074 d MC33071...
This transmitter emits signals in the FM range, reaching a few meters away. The modulation...
The consumption of this circuit in the standby condition is only 1 uA. The circuit must be...