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.
Found in American documentation, this circuit is more sensitive than the previous one, as it uses...
This amplifier with differential input uses two old op amps but can be implemented with modern op amps....
We found this circuit in the Linear Applications Handbook of the National Semiconductor of 1994....