Yes, it is possible to use a Cisco 7940 or 7960, however the stock phone will not work without being flashed with Cisco SIP Software. It comes defaqult with Cisco proprietary SCCP software. This SCCP protocol will only work with Cisco Call Manager.
In most cases updating the software is a relatively easy process but getting the software is normally done through Cisco and requires a Smartnet Contract.
The following process is a requirement before any firmware upgrade is done with a Cisco IP Phone.Boot up your phone. You can use either PoE or a power supply. I used a power supply without plugging any internet connection. It will display “Ethernet disconnected.” You will just then wait for it to boot up. It might say “Configuring CM List“.
Press Settings -> Firmware VersionsUnder Application Load ID, you will see your firmware version.
It looks something like P0S3-8-12-00 , this means version SIP 8.12.
- The third character which is “S” stands for Session Initiation Protocol (SIP). It could be “0” for Skinny Call Control Protocol (SCCP) or “M” for Media Gateway Control Protocol (MGCP).
- “8” represents the major version.
- “12” represents the minor version.
- “00” represents the subversion.
SCCP firmware: P003xxyyzzww: where x represents the major version, y represents the major subversion, z represents the maintenance version, and w represents the maintenance subversion.
SIP firmware: P0S3-xx-y-zz: where x represents the major version, y represents the minor version, and z represents the subversions.
You can also see the Cisco Article on finding your software versions by clicking How to find your Cisco VoIP Software Version