Ok I stand corrected, I originally said the Aries styled centrex sets that replaced the Delta series centrex sets were introduced in 1995,96. From this brochure I found, these M5000 centrex phones with the Meridian 1 styling were actually introduced in 1994. This is one thing that actually confused me about Nortel. While the similar styled Meridian 1 M2000 sets weee introduced in 1989, it took almost five years to release the same styling for the also very common P Centrex phones, such as the one in this brochure, to be introduced.
The big difference is technology. While the Meridian 1 M2000 phones were solely designed for PBX use and were fully digital, the Centrex sets are a hybrid of analog and digital signaling designed for both public and private systems to work on the much larger public DMS-100 and private SL-100 switches.
These sets are still manufactured by Mitel, formerly Aastra which acquired the manufacturing of these sets in 1999.
Can you tell the difference between these M5000 sets and their fully digital cousins the M2000 sets? It’s the triangle under the Meridian logo. For some unknown reason the red triangle was never activated for Message Waiting indication on the M5000 sets. Notice it’s blanked out in the photo on this manual. Instead a dedicated MWI button was required on one of the feature keys, and the LCD button would show a blank triangle on the LCD panel when a message was left. It’s a mystery why you could do a red MWI on analog sets and digital sets but not on the Centrex sets.