The Smart Phone Control Protocol (SPCP)
The Smart Phone Control Protocol, or SPCS, is an addition to the Simple Call Control Protocol (SCCP) that is only supported on the CP-500 phones and the SPA525 phone.
79XX phones register with their SCCP call control using a proprietary handshake that consists of a series of messages. During the registration phase a number of things happen:
1. Phone (Station) sends a Registration Request
2. Request is acknowledged by the Call Control (CME/UC500)
3. Capabilities are advertised
4. Button template, Softkeys, Line Status, Display message, Speed dials Time and date are requested by the phone and sent by CME/UC500
When the phone is a 500 series phone, two additional messages precede all this handshake, namely an SPCP Token Request and an SPCP Token Acknowledgement (if successful) or Token rejection (if unsuccessful). A Token ACK can only be sent by UC500, while an ISR will always send a Token Reject. This prevents the phone from registering to any call control different than UC500.