With IPHost Network Monitor you can run WMI Active Lines monitoring of various devices in your network.
To create a WMI monitor for Active Lines, provide host name (it must be a Windows host) and specify custom WQL query:
The number of telephone lines serviced by this computer that are currently active.
The Telephony System
IPHost Network Monitor is an advanced and easy tool for monitoring LAN and WAN networks, network servers, workstations and TCP/IP devices. Use IPHost Network Monitor to monitor your servers, domains, computers and devices.