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  1. Technology
November 24, 1988


By CBR Staff Writer

If a large firm were to approach an independent telecommunications consultant and ask for advice on which supplier’s PABX to buy, no doubt one of the topics up for consideration would be how each vendor’s equipment was geared for the emerging Integrated Services Digital Network. But if the choice of system were being made on this criterion alone, the customer would still be not very much the wiser, as the strategies of most of the PABX manufacturers seem to be very much of a muchness, generally including what Richard Kee, consultant and author of the Ovum Ltd report on ISDN: Customer Premises Equipment calls odds and sods behind their PABXs, and a vague commitment to ISDN. And even this can be taken with a pinch of salt – at least until user demand or new entrants to the market begin to make the matter more pressing, and cause the suppliers to put their money where their mouths are. Something different So is there very much to choose between the systems at the moment, and do any of the suppliers stand out from the crowd? One that does seem to have something different to offer in the long night before the dawn of ISDN is L M Ericsson Telefon AB, which is currently claiming to be eating into its rivals’ market share with its MD 110 pulse code modulation digital switch. Not that Ericsson is one of the market leaders – it currently rolls in sixth in the league table of PABX suppliers in Western Europe – but what it does do is offer a system with a modularity that it claims to be unique, and in a market where many of the distinctions between models seems to be on the basis of what they might do in five years’ time, Ericsson is at least doing something different in claiming a distinction that is current. The MD110 is one of the new breed of PABXs – sometimes known as an Integrated Services PABX because they are designed to handle whatever ISDN – when it arrives – will throw at them. Three models are on offer, the MD 110/20 for 40 to 160 extensions; the MD110/40 for 80 to 600 extensions; and the MD110/90 for between 200 and 10,000 extensions. Like the majority of its competitors, Ericsson has yet to offer both primary and basic rate access in terfaces, although it has both on trial at the moment, and in the meantime is operating its own proprietary pre-ISDN interfaces. The proprietary interface uses a burst mode transmission signalling technique, supporting one 64Kbps channel for speech, and one 9.6Kbps channel for data, with a separate signalling channel for control over a single pair of wires. A distinction that needs to be made here is the fact that although the decision to opt for primary or basic rate access is very much dependent on which of the two the national phone company opts for, the data rate on the customer’s side of the PABX – the internal operating rate – provided by some suppliers already conforms with CCITT specifications. For instance, the Philips NV and GEC Plessey Telecommunications offerings each support an internal speed of 144Kbps – comprising 64Kbps for speech, 16Kbps for data and 16Kbps for signalling making the Ericsson option seem a little elderly in comparison. Working with the MD110 is a range of digital terminals including a featurephone with RS232-C data terminal socket, a number of terminal adaptor units, including one which enables an MS-DOS micro to be connected in to the MD110, and co-ax asynchronous converters which enable IBM 3270 terminal systems to communicate via the PABX. Unlike some of its competitors, MD110 also conforms to the British Telecommunications Plc standard for private wide area digital networking, the DPNSS Digital Private Network Signalling System and the DASS 2 Digital Access Signalling System, public standard. But getting back to the MD110’s unique feature – its modularity it is the only PABX sold on the basis that it is a distributed system. Basically it consists of two types of unit – a group switch, and a line interface module. The interface modules are microprocessor – controlled units that can function either as an autonomous PABX or as an integrated part of a l

arger system. Each 200-extension interface module can be connected to others, providing a system that Ericsson product manager Karl Erik Elfgren claims is ideal for distributed sites such as University campuses, hospitals and public utility boards. In effect, this gives the user the PABX-to-PABX communications advantages of ISDN ahead of time. As John Lane, consultant with Butler Cox & Partners explained, this would not be totally impossible with other vendors’ equipment, but it would be more expensive and more difficult because their basic building blocks – or equivalent to the Ericsson line interface modules – are much larger. The MD110 is ideal for installations that require a network of small PABXs, and it has sold well into those kinds of sites. However, for organisations that have a higher extension-per-site requirement, the system does not work out quite so well. One user, who preferred to remain nameless said, The problem of using the MD110 as a distributed system is that you can only have one group switch. So every interface module has to be independently connected to the group switch, making an additional requirement for a Megastream connection. While the Ericsson system allows users to do economically on their private networks what they will ultimately be able to do on the public network with ISDN, then surely the arrival of ISDN will obliterate one of the major selling points of the product? Terry Henson, director of private switching for Thorn Ericsson, claims that when that happens, the MD100’s modular architecture will still be an advantage. While many other manufacturers will be introducing a whole new generation of PABX before ISDN finally arrives, Ericsson is committed to the MD110 architecture. Because it extends right down to board level, the concept of a modular design means that the same architecture can handle ISDN and whatever comes after it. Secondary to the AXE Another issue of interest to potential buyers is that of support for the product within Ericsson. According to Elfgren, the MD110 accounts for only 10% of corporate turnover, a small amount compared with the business Ericsson derives from the AXE public telephone exchanges in their various incarnations. To observers such as Ovum author Richard Kee, MD110 development must be secondary to what Ericsson is doing with its public switch, and any future alliances on that front would inevitably affect the direction taken in private switching: Partnerships at the AXE level will be much more important to Ericsson, and the MD110 could well find itself swept along behind.

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