Experience gained from the implementation of DASS and DPNSS

Before dealing with the experience of the application of DASS and DPNSS and their differences a summary of the history and a general description of these signalling systems is given. The Digital Access Signalling System (DASS) was conceived in 1981 as the signalling system for the Integrated Digital Access to the public telephone network in advance of any internationally accepted standards. DASS is designed to provide signalling service both to basic rate access and to primary rate access users. DPNSS was conceived during 1983 as a signalling system to enable large corporate network users to create a `private ISDN´. The DPNSS specification was developed by a number of parties with the intention of creating an `Open System´ such that a number of implementations could be seen to work together, offering the customer the freedom to choose the `best´ PABX/ISPBX to meet the specific requirements of a given site. As a long term aim this has been achieved by careful specification to allow flexibility