The first medium-to-large scale telephony system I supported was on behalf of a company that provided enteprise IT systems and support to global clients. The telephony system was also used as a feed in to the in house call centre operated by the Service Desk operation and also public facing UK Gov contracts. My involvement included supporting, upgrading and maintaining the IVR system aswell as hunt groups and call routing functions. User managment was conducted by first line in the first instance. This involved me covering my role that i was employed for plus any escalation for the telephony system. The software that was being utilised was Storm by ContentGuru. I haven't worked or used any "old school" type telepohony systems for years, the choice seems to be for a cloud based solution. I can still desgin and deploy these systems when called for, even if the technology is slowing wilting.