Has anyone came across an idea similar as follows;
Simple home telephone system with 1 input line. Using home run wiring (a wire to each phone returning to a closet or similar place) and regular analog phones, creating a system that could be interfaced with a front entry intercom, shop or outside intercom, paging feature to other phones, etc.
The idea is to design something simple that would, upon picking up a generic phone and dialing a specified key sequence (like #*1) the user would hear a beep or something that would indicate that the system was accessed (at that time, that particular phone would be isolated from the incoming phone line).
Any info would be helpful. Thanks