DPNSS

The Digital Private Network Signalling System (DPNSS) is a network protocol used on digital trunk lines for connecting two PABX. It supports a defined set of inter-networking facilities. DPNSS was originally defined by British Telecom.

DPNSS was developed in the early 1980s by BT in recognition that the emerging Digital Private Circuit Primary Rate product 'Megastream' had to address the market for both data and Voice. At the time 'CAS' inter node signaling was slow and inter-register signaling MF5, developed for the PSTN was complex and would not support sufficient features.