I've used Bogen and Valcom for multi zone paging. The last I used was a Bogen. It will allow a CO port,analog station port, or page port for access. I feed it from an analog station port. To page, I programmed a speed dial code to dial the analog station port. It rings and the Bogen answers immediately and provides a beep tone. Then one dials the page zone code, one of which is an "all call". This Bogen unit has up to nine zones if desired.