Pictured at my favorite hospital where all of my parents were treated with great care and where I volunteered at, is a Nortel M2616 working on a CS1000 former SL1 switch.
I used to volunteer at this great hospital during the 1990s while they had two different PBXs, a 1a2 arrangement and a Northern Telecom SL1, both systems were tied together.
The operators page occasionally through the switchboard into a Dukane All Call System and the paging sounds ultra crisp and clean as well. There are also some separate page zones in other areas of the hospital.
This particular phone is in the radiology area where I used to volunteer. Notice the Page button. This was used for a paging zone only within the radiology area. I used to page with it constantly on the old SL1 wedge sets. The old style G handsets on the Q series SL1 sets would make the most obnoxious suction noise when I hung them up over the speaker without pressing RLS. The ladies would tell me to press the mislabeled Ris button. For some reason Northern Telecom sent out a whole bunch of button labels that said Ris instead of RLS. Debbie in Xray used to tell me to use the Ris button to end pages. It’s RLS for release. I had such a blast volunteering at that hospital!