Nortel (Avaya Blue)
Nortel M522 Add-on Expansion Module for Centrix, NT4X43AA93, Gray, New
The Nortel M522 add-on expansion module is designed to work with the Nortel Meridian Centrex M5216 and M5316 phones. The M522 (NT4X43AA) adds an additional 22 programmable buttons to your phone to be used as line appearances, extensions, or feature keys. The LCD indicators inform you of the status of each line.