The Deskmate (and any Leitner and Sennheiser corded headset) will work with existing M22 amps by Plantronics.
The key is to use the Sennheiser Quick Disconnect Cord for Cisco Phones connection cord (catalog # 1788 on website, part # 005365) . For the Leitner, it will work great right out of the box!
You may need to adjust the compat or volume settings on the M22 to ensure that the sound quality will be optimized
First test the compat setting recommended for the phone, if that’s not giving them optimum sound - try each setting.
(415) 351-5857
kyle@headsets.com