David Bowen on the powerful computers that help to run the telephone ne twork
British Telecom's computer system has received unwelcome publicity recently, thanks to the actions of an assiduous computer hacker. But the main impact of its Customer Service System (CSS) has been both more welcome and more mundane: it has broug ht unwonted efficiency and has helped prices fall by 40 per cent since privatisation 10 years ago this month.

The CSS, which started operating in 1987, consists of a network of 60,000 terminals on interlinked computers that should, in theory at least, give BT's customers unrivalled support. The information stored on it, if written down, would take up 50 miles ofshelving. The system handles 14 million messages a day.

Say you want a new phone line. You ring 150 - or 152 if you are a business customer - and are put through to a customer service centre. The operator on the other end of the line will be using a screen that is hooked up to one of 11 powerful mainframe computers - IBM 3090s - which are in turn connected to 50 other computer systems. As the order is punched in, signals are sent out to the systems that need to know. A line is allocated, the engineers are notified, the directory computer is updated, a contract is sent out - and information is passed on to the marketing division, so that it can try to sell you more services.

If necessary, the computers will send information back to the CSS operator: the engineering system might, for example, reveal that there is a technical problem with an exchange. BT handles 70,000 orders a day. Only about a thousand are for new lines; therest are for other products or pricing plans.

Dial 151 or 154 to report a fault (as 42,000 people do every day), and you will find that the operator knows what BT equipment you have, and can test the line immediately (in fact, every telephone line is tested automatically at night without our knowing, so many faults are mended before we have discovered them). Most important, from an engineering point of view, the system shows what sort of connection there is between the exchange and the house - so the operator can say whether a visit will be necessary.

Perhaps most useful, the system is designed to track problems that cannot be sorted out immediately. BT says it will repair a domestic phone line within 48 hours, and the CSS will flag up delays, so that they can be chased before the deadline is passed. It will also keep a sort of doctor's notebook: an operator will be able to see what contact there has been with the customer and whether there have been problems before. So you should find the operator is comfortingly well-informed about you and your line - and if the company denies ever having heard of you, you can demand a printout of the log that shows your 11 previous calls.

If you want to stop BT sending out bills, you need only sabotage three print centres, at Gateshead, Milton Keynes and Cardiff, which process 400,000 bills a day between them. The information for each bill is held initially in local exchanges. It is then

passed on to the CSS, which stores it until it is time to send the bill out. It is then transmitted to a print centre, which prints it, puts it in an envelope, and stacks it in postcode order. CSS also ticks payments off when they are made, and sends ou t reminders if they are not.

All this automation has had its effect on jobs. BT has lost 100,000 of its 250,000 staff. Most of them have been engineers, made redundant by the replacement of mechanical switching equipment, but a good few did the clerical jobs the CSS has now taken over. Just as there are now only three print centres, so the other functions have been concentrated. There used to be 29 CSS computers, one for each region; now there are 11 and the number could fall further. We have yet to see what changes the discovery that it is not hacker-proof - and may therefore need an overhaul - makes to this process.