When British Telecom postponed its launch of a Centrex service, which had been planned for last month – and simultaneously cancelled its order for an AT&T-Philips exchange on which to run it, it looked like a big setback. On the contrary – the delay was because Telecom now has much more ambitious plans for the Centrex concept, plans that revive a decade-old dream that was once a driving force in IBM’s plans for the future.
The revelation that GEC and Plessey are implementing Centrex software for the System X digital exchanges (CI No 869) could significantly improve prospects for sales of the exchanges in developing countries. There are scores of companies in countries like India that would love to have the facilities of a modern PABX but are precluded by import and hard currency restrictions from doing anything about it. And while those restrictions are unlikely to be relaxed any time soon, the possibility of the national telephone operator increasing its revenue base by providing such services on a centralised virtual PABX basis is a much more realistic prospect. But British Telecommunications Plc’s emerging ideas for Centrex are rather different. In April, the phone company plans to reveal a revolutionary approach, involving not only a virtual voice PABX systems, but support for nationwide high speed data networks, right down to virtual local area networks, complete with transparent virtual gateways to wide area traffic and public services. These extensions were relayed in a specification passed to the developers of both System X and System Y, and are being incorporated into new Centrex software for digital switches. GEC and Plessey both have confirmed that they are in receipt of orders for Centrex capability on the System X exchange, and they are working together to design the software that will make this possible. New facilities Plessey confirms that there are a host of new facilities to do with managing large company-wide data networks within the specification, but will not go into detail, although it commented that the facilities envisaged are not available in any existing Centrex system. The bad news is that the System X version is not likely to be ready much before 1990, and the System Y supplier, Thorn-Ericsson, is believed to be further along in the development process, writing its software for Ericsson’s AXE exchange. A Centrex service is the creation of any virtual piece of equipment on a public telephone exchange, although it is traditionally associated only with virtual PABXs. These can be appropriate in a large company that is continuously upgrading and changing its telecommunications infrastructure, environment, but British Telecom has been worried that existing services cannot supply the sort of flexibility, programmability, resilience and security that users have come to expect from a digital PABX. It also wants a system that can be transparently integrated with all those PABXs already installed with customers. It insists that it should not be a voice-only system, it must carry data; it should not be site based but offer company-wide facilities, and it should be reconfigurable in a 24-hour turnaround to suit exact customer requirements. What other new services does British Telecom envisage? One example given at a Telecom presentation referred to an established local area network user moving location within a company. Under the new system, he would be able simply to take his terminal with him, tell his Centrex contact that he had moved, plug directly into a digital phone line, and carry on as if he had never moved. Not many local area networks can be reconfigured that fast, and there’s no reason why it could not extend beyond the normal re-routing distance for that local network. To handle this type of company-wide data traffic, Centrex would have to incorporate multiple protocol conversions, and offer advanced encryption. Older readers may find the concept ringing loud bells in their heads: back in the mid-1970s, the most inveterate IBM watchers used to mutter darkly to each other about The Plug – actu
ally a socket – in the wall, to which IBM hoped to be able to deliver every computing and communications service within a company impartially. The Plug, seen at the time as another of IBM’s megalomaniac ideas to rule the computer world, became bogged down in local area network standards and IBM’s failures to make an impact in the telephone world, and has never seen the light of day in any coherent form even the IBM Wiring System, which was a vestige of the Grand Strategy, has proved a big disappointment for the company. But it could just be that British Telecom is preparing to turn a failed IBM idea into a commercially viable proposition with its Centrex. Do not exist Another task for the for the Centrex software teams will be to interface Telecom’s existing standard PABX network management facilities to its public switches, giving them the ability to treat a Centrex virtual PABX as if it were a separate unit. This system runs on a Concurrent Computer 32-bit minicomputer, fed by multiple Z80s, with the software written by New Jersey firm Avant-Garde Computing Inc. This deal was signed up in 1986, for its packages WatchMan, LinesMan and GuardsMan, which monitor performance, response times and usage, help with budget planning and handle password protection services. The only major issue left unresolved in Telecom’s Centrex plans is whether or not it will be worthwhile to offer an interim solution. Given the fact that the only digital exchange on offer which both has Centrex and has been adapted to UK standards is the Northern Telecom DMS series used by British Telecom’s one domestic competitor, Mercury Communications, the UK phone giant faces an awkward decision. Its thinking on Centrex made a quick U-turn when a market research exercise uncovered a strong undercurrent of desire for ‘modern’ Centrex facilities, which Telecom says do not yet exist anywhere. It was this abrupt about-turn that lead the telephone company to drop its plans to introduce a service last month based on the Number 5ESS switch from AT&T-Philips Telecommunications (CI No 848).
