have Nortel compact ics that lost battery and programming. change battery, reprogram system and added all phones on answer DN for station 21 to have door bell ring all phones. works great. line two on phone system is a fax line but put on system to have another line when not in use. it is set to app only so not to ring. when that line rings after couple of times, it starts ringing on set 21. it show line 02 to prime set 21. i turned off the prime set number for line two and that worked but after that no door bell ringing on any phone. there are no lines on the DN for door intercom device. set up per program instruction on all setting. why are these two issues tied together. there is only an intercom set for prime line on the door DN. any suggestion thanks