Our VoIP service is based on SIP (Session Initiation Protocol, RFC3261), an open-standard signalling protocol that is almost universally supported by telephony devices and manufacturers. All Yealink and Grandstream devices, as well as nearly all Cisco devices, support SIP.

Some manufacturers, as part of offering integrated communication solutions (such as PBXs and telephony devices), use proprietary signalling protocols, such as SSCP, which is implemented in CUCM (Cisco Unified Communications Manager) for communication between endpoints and the PBX.

As a result, phones that are factory-configured to operate with CUCM, such as the Cisco 7900 series (7965, 7940, 7941, 7945, 7935, 7975, 7911 and others), are not directly compatible with our service. To use them with our service, you will need to replace their factory firmware with one that supports the SIP protocol.

You can find more information here, while the SIP Firmware for the various models is available here.

The procurement of the above-mentioned devices and any firmware modifications are the responsibility of the customer and are not related to modulus. For further information, we recommend contacting the manufacturer (Cisco).