As HDLC can operate successfully in quite poor (errored) data environments, DPNSS will work over a 2Mbs link running without proper synchonisationsynchronisation (plesiochronously) and over poor quality connections (including badly terminated connectors). When setting up PBXs to run a DPNSS connection one end must be defined as the primary or 'A' end. This is a protocol requirement and has nothing to do with link synchronisation. However, such badly synchronised links were frowned upon because of the problems associated with sending faxes and/or other modem based communication which were not specifically identified within the protocol.
==DPNSS and VoIP==
Line 43:
==External links==
* [http://www.niccstandards.org.uk/files/current/nd1301_2004_11%5B1%5D.pdf ND1301:2001/03, The DPNSS specification at NICC]
