This screenshot shows the console that I used when I was an operator at Purdue University from 1995-1999. This console is the main switchboard terminal that works off the DMS and SL-100 platforms. Unfortunately the more feature rich M2250 console doesn’t work on the DMS or SL-100.
This set used a single line LED display similar to a Texas Instruments 1970s calculator. A wildcard button allowed you to change the ring tones from continuous beeping to single beeps.
Purdue no longer uses these, in fact they don’t have an operator anymore either. All calls get answered by an auto attendant and the IT people.