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November 17, 1988


By CBR Staff Writer

British Telecommunications Plc’s announcement late last month that it has a primary rate Integrated Services Digital Network service ready for public use will do much to stave off criticism that the company’s ISDN efforts are dilatory, but it offers nothing immediate to the user. Called Multiline Integrated Digital Access – known more familiarly as IDA – the service consists of 30 channels of 64Kbps capacity for voice and/or data traffic plus a further channel dedicated to signalling. Customers will eventually be able to use this 2Mbps Multiline public pipeline to connect digital PABX networks using a compatible signalling system, extending their private networks into virtual webs capable of carrying data, high-speed facsimile, graphics and video. This is an attractive scenario, especially when the virtual network spans Europe and the rest of the world, in theory at least. But the path to realising such global harmony is fraught with the usual problems of co-ordinating standards – and ISDN on even the more modest national scale will be frustrated for some time yet.

Delays Mutterings from the industry that ISDN will offer too little and too late meanwhile grow louder. The arrival of Multiline Integrated Digital Access in the UK illustrates the nature of the domestic delays, which are likely to be repeated throughout Europe. Multiline IDA is rendered impotent until suppliers of digital PABXs obtain approval for signalling connection to the public ISDN network. In the UK, this will be achieved by a signalling system developed by Telecom called Digital Access Signalling System or DASS 2, which makes the link between digital PABX and the public digital exchange, and is designed to switch the higher level voice and data facilities such as call-party identification and call-back-when-free. In fact, compatability problems with the Digital Access Signalling system 2 and System X software at the local exchange end have taken months to iron out, and Telecom’s launch date for Multiline was delayed by one year. Not surprisingly, GEC Plessey Telecommunications Ltd, manufacturer of System X has been the first to achieve DASS 2 compatibility on the PABX side with the ISDX switch gaining approval a couple of months ago and the GEC-inherited ISLX expected to follow suit shortly. Ferranti International says it hopes for approval soon while Mitel Corp anticipates a Digital Access Signalling 2 offering in April or May next year.

The delay has been a source of anger for those users who decided to go with Multiline early on and moulded a communications strategy around the product. British Steel was the first off the mark and bought the service in advance at the time of announcement. One year later, the company is still waiting for a glimpse of the benefits. And according to Grant Broster, marketing manager at Mitel, facilities available on the first version of DASS amount to next to nothing. Direct dial-in is provided but users will have to wait for the second release of DASS to catch the first glimpses of call charge and call party identification. Mitel considers the present content dubious and is waiting for the enhanced version before attempting to woo the public. Broster would also like to have more assurances from Telecom about the future ability to siphon off Multiline channels for private networks. But even as DASS 2 software gradually becomes available across a variety of digital PABXs, access to international ISDN for UK users will not be free of hitches. The software has been developed by British Telecom in advance of the final ratification by the Consultative Committee on International Telephony & Telegraphy, CCITT, of its No 7 signalling channel. Like other European PTTs, Telecom has built a proprietary subset or optimisation of the CCITT version and Alan Knight of Logica Plc anticipates a great deal of incompatability at the higher levels when switching between different national exchanges. A number of these national flavours of ISDN are planned on the continent with activity stepping up in 1989. France is operating a

pilot in Britanny for basic rate ISDN (two voice+data channels plus one for signalling) which will be ramped up to include primary rate ISDN in the middle of next year. Meanwhile the Deutsche Bundespost is introducing 1,000 lines of both services on a pilot basis into eight cities beginning in Hamburg this month. All PTTs are trying to get a service to market as quickly as possible to whet the public’s appetite: inconsistencies will be tackled as they arise.

Tariffing Tariffing will be a key factor in triggering demand. Traditionally, different rates are charged for voice and data traffic but ISDN treats all traffic as a stream of bits. Any bias towards voice or data charges could dampen interest. The PTTs have shown a greater willingness to co-operate over this issue. France, West Germany, Italy and the UK have signed a quadrupartite agreement to co-ordinate their tariffs to establish a competitive edge over equivalent public switched telephone network charges. However the sample prices being touted by Telecom for its Multiline Integrated Digital Access will sting those customers not already connected to Megastream with prices in some extreme cases topping the UKP500,000 per annum mark. Until the second version of the Digital Access Signalling system materialises – June 1989 at the earliest – there seems to be little incentive for customers to move over from the switched network, and users will likely have to wait until the 1990s to have ISDN at their fingertips.

For confused users wanting to distinguish the facts from the flannel, and invest in a system that will be able to cope with whatever benefits ISDN may bring, help is at hand in the form of the ISPBX Specification, a document published by the ITUSA that gives guidelines to purchasers on the kind of questions to ask suppliers pertaining to standards, upgrade paths and so on. The ISPBX Specification is UKP200.

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