Hi. we have the nortel m7324. one of our incoming lines rings then turns into a fax machine sound. Any ideas on how to fix this? we answer calls for a number of different companies, so this is really bad. no luck with at&t. we thought it started after having a power outage.

Office Equipment & Supplies - Nortel - Norstar M7324 Telephone NT8B42: Norstar Central Answering...