When you design equipment that interfaces to a phone line, it is often desirable to be able to monitor the dc voltage on the line. This ability can be useful, for example, to determine whether a line ...

The circuit was designed to provide a monitoring scheme for a telephone line where several phones are installed, to indicate when one is being used. 4N25 – a general purpose optocoupler that consists ...

I am helping a friend who is having horrible dialup problems. He is lucky to stay connected for 10-15 minutes at a time. This problem has continued through several modems & at least 2 computers. He is ...