I think he's asking how to keep people from _deliberately_ playing touch-tones over the paging system when they dial the PA access code from their phone. In other words, they've probably got some pranksters in the fire station who like to pretend they're the organist for Deep Purple, using the PA as their amplifier and the Touch Tone keypad as ntheir organ.
A ham radio operator would be the best guy to ask, since hams have been using Touch Tone on FM repeaters for a while now. The only question would be if Tom H is trying to hang up on any PA access call that has Touch Tone in it, or if he wants to just mute the tone and keep the call active.
William[TELECOM Digest Editor's Note: Maybe you are right. I used to see (or actually hear) this happen a lot in Chicago at the Transit Atrocity stations. The overhead loud speaker would come on, which was _supposed_ to be for an announcement from either one of the control tower operators, or some other employee. When the loud speaker came on, all you would hear was 'dee, dee, dee, doop' and then a hang up. Obviously someone had pressed the wrong key on his multiline phone or had started dialing without looking to see which line key was pressed down. PAT]