Currently, UCM can detect poor call quality or issues with call setup but what if the phone itself
is unable to send data to the call manager (Avaya and Cisco).
For Cisco - If the phone was at one time registered to a Call Manager, then it's status will change to "Lost Contact".
For Avaya - You would need to look at the last activity time to get an idea if the phone wasn't in use. However, it couldbe that no one is using the phone. For Avaya we only monitor the phones when they make\receive a call.