Last year. Someone else bought the phone system in 2016 and it was based on a 12 year-old design implemented in modern hardware.How long ago ?
If your using PBX still, your about 3 centuries behind.
I suggested VOIP but it cost about $100 more per station and didn't save much recurring money.
Maybe its me (but its probably Cisco) but VOIP feature phones are stupid expensive and the idea of incorporating desktop computers into the phone system has always given me the willies.