When the phone rings, a high-powered incandescent light comes on. This circuit can be interesting to obtain the remote call warning or to assist the hearing impaired.
We found this amplifier in a publication of 1990, but it can be mounted today with some exchanged...
This circuit, which is also a leak meter, has a detection resistance of billions of ohms. We found...
This circuit was found in an American publication called Ham Radio. The circuit uses still current...