digital private network signalling system (DPNSS)

The Digital Private Network Signalling System (DPNSS) is a standardized protocol developed by British Telecom and well-known PBX manufacturers for networking digital PBXs.

DPNSS was developed before ISDN was completely standardized and before the Q-Interface Signalling Protocol( QSIG) existed, whose development was influenced by DPNSS. There are also interworking specifications for the two systems.

DPNSS is a protocol that supports communications between multiple PBXs over ISDN as well as many telecommunications services. The DPNSS specifications include about 50 services and functions. These include automatic callback, call forwarding, call waiting, conference calling, route optimization, call hold, etc.