Science: Phone-in frenzy made BT see red: Its futuristic nerve-centre can't always stop the network jamming. Susan Watts reports

WHEN hundreds of thousands of excited couch potatoes rang their favourite television talent show to place their votes, it paralysed British Telecom's network in Greater Manchester, Cleveland and parts of Scotland. It was BT's worst crash.

The company claims that within half an hour of the mass phone-in to the Granada Television show Stars in their Eyes three weeks ago, the network was back to normal - but last week it refused to say how many lines were out of service, and for how long. Most seriously, some customers of affected trunk exchanges would not have been able to get through to the emergency services. The company is conducting an urgent internal inquiry to find out exactly what went wrong.

BT had provided 10,000 lines for the event, but there were more calls than even Granada had anticipated. 'We had over 10 million call attempts, over 80 per cent of which were made during a 15-minute period,' a spokeswoman said. She added that the presenter of the show sought to raise the drama by encouraging people to wait until the last possible moment to call.

Most of the call attempts would have been the result of frantic fingers pressing recall buttons over and over again. BT had to introduce a procedure called 'call-gapping' to filter out all but a certain number of calls, at random, every second.

BT would not comment on whether the problems affected the result of the show. 'Granada is sticking with its result,' the spokeswoman said.

The timing of the incident was unfortunate for BT's image-makers, coming just four days after the company invited journalists to its high- security network management centre at Oswestry, Shropshire. From there, managers control every exchange on Britain's network - plus overseas links - changing the way they handle calls to overcome or avoid congestion. Network controllers maintain a 24- hour vigil in front of vast maps of the telephone system displayed on a wall of video screens 10ft high and 70ft long.

The television talent show, like charity appeals and disaster information lines, was exactly the type of situation the Oswestry centre is designed to handle.

The BT spokeswoman said it is still not clear exactly what went wrong. In a statement last week, BT said: 'There are technical limitations on the capacity of any network. Clearly there are also limitations on the network management centre's ability to implement call-gapping controls within such a short time-scale, given the volume of calls.'

The spokeswoman said that the wave of calls overloaded a number of local exchanges. Within seven minutes controllers moved to protect the rest of the network, stepping up call- gapping from a setting that allowed one call every fifth of a second to one just every four seconds.

Journalists shown around the Oswestry centre saw the result of a slick public relations operation. The women wear blue spotted blouses, men the corporate tie. John Davies, the centre's customer relations manager, said this 'image clothing' helps to show visiting customers that it is 'a clean and tidy operation'.

To the journalists intrigued by rumours that the Oswestry centre is the focus of MI5's telephone tapping activities, the visit yielded no clues. Mr Davies said: 'We do not carry out telephone tapping from here. There must be some confusion over the use of the word surveillance.'

Last month's crash was not the first time that Oswestry has been caught out. In July 1990, barely a month after the first batch of prestige customers was shown around the centre, Tina Turner fans caused a similar, more limited crash in the Bristol area.

An advertisement in a national newspaper had promised free tickets for a Tina Turner concert to fans who bought a bottle of cola, slotted two digits from its barcode into the gaps in a Bristol telephone number and rang between 6pm and 7pm. Shortly after 6pm on 24 July, the patch of 'video wall' at Oswestry covering the West Country burst into life. Red alarm lines sprouted around Bristol.

The Bristol-based company that had taken out the advert had laid on just 10 telephone lines. Within a minute, hundreds of thousands of devotees were trying to ring in.

As far as the company knew it was receiving about 50 calls every quarter of an hour. What it did not know was that in the same period, around 200,000 calls were failing. Exchange after exchange was hitting its maximum call capacity and giving up. Call-gapping again saved more of the network from disaster.

Since this experience, BT has been encouraging television companies to warn them if the network is likely to come under stress because of a programme. It coped with more than two million calls in the five minutes following this year's Song For Europe contest, when viewers rang to pick the British entry.

The Oswestry centre checks the state of each exchange or 'switch' and keeps track of how well it is transmitting to the others. It also monitors the volume of traffic that is ebbing and flowing through the arteries and veins of the network.

More than 80 per cent of BT's network consists of optical fibre. Each one-inch thick cable, carrying 96 fibres, can cope with up to 370,000 simultaneous calls. A minimum of two lines run from each digital local exchange to the trunk network, providing extra protection.

If a call fails to get through after a certain number of attempts, the exchanges (which are 'semi-intelligent') automatically send the call via a less congested route. Just as the local exchanges replace the rows of women telephone operators of Victorian times, Oswestry replaces their supervisor, guiding an exchange on how to redirect a call if an exchange's choice fails.

Computers at Oswestry fire off 'queries' to telephone exchanges around the country, asking each, in digital code, how it is performing. Over a two-minute period, the centre gathers performance data from more than 700 exchanges. During the following two minutes it analyses this data to see how traffic is faring. This data is displayed on the 'video wall' at Oswestry.

The video wall, made up of a patchwork of 140 video screens, is fed by red, blue and green rear projectors. These illuminate the branches of the network to draw the operators' attention to a problem. A red connection is the most severe warning, ranging through orange, yellow and green to blue, for the least serious fault or congestion. Lines linking exchanges appear coloured along only half their length, stretching from the end experiencing difficulties.

Congestion could mean three or three hundred calls are failing, so operators consult a database to find out the exact number of calls in difficulty. They then ring through to a local exchange for clues to what is going wrong and whether the problem is a technical fault or overloaded lines.

Most of the fault detecting and fixing takes place at three subsidiary network management units around the country, while Oswestry concentrates on overall management of the network and international links.

Procedures put in place after the Tina Turner incident were supposed to stop anything similar happening again. Yet it did, and dramatically. The company's internal inquiry into the talent-show crash should yield results in the next few weeks.

What is already clear is that liaison must be improved so that everyone is aware of the limitations of BT's network. And BT must be big enough to tell television producers that it simply cannot meet some requests - for the sake of the rest of its customers.

(Photograph omitted)

Start your day with The Independent, sign up for daily news emails
ebooksA year of political gossip, levity and intrigue from the sharpest pen in Westminster
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Ashdown Group: Junior Web Developer - Kent - £40,000

£30000 - £40000 per annum + benefits: Ashdown Group: Junior Web Developer - ne...

Recruitment Genius: Production Team Leader / Chargehand

Negotiable: Recruitment Genius: A vacancy has arisen for a Chargehand to join ...

Ashdown Group: Client Services Manager - Relationship Management - London

£30000 - £32000 per annum + benefits : Ashdown Group: A highly successful, int...

Recruitment Genius: Credit Controller / Customer Service

£18000 - £20000 per annum: Recruitment Genius: This rapidly expanding business...

Day In a Page

Syria crisis: Celebrities call on David Cameron to take more refugees as one young mother tells of torture by Assad regime

Celebrities call on David Cameron to take more Syrian refugees

One young mother tells of torture by Assad regime
The enemy within: People who hear voices in their heads are being encouraged to talk back – with promising results

The enemy within

People who hear voices in their heads are being encouraged to talk back
'In Auschwitz you got used to anything'

'In Auschwitz you got used to anything'

Survivors of the Nazi concentration camp remember its horror, 70 years on
Autumn/winter menswear 2015: The uniforms that make up modern life come to the fore

Autumn/winter menswear 2015

The uniforms that make up modern life come to the fore
'I'm gay, and plan to fight military homophobia'

'I'm gay, and plan to fight military homophobia'

Army general planning to come out
Iraq invasion 2003: The bloody warnings six wise men gave to Tony Blair as he prepared to launch poorly planned campaign

What the six wise men told Tony Blair

Months before the invasion of Iraq in 2003, experts sought to warn the PM about his plans. Here, four of them recall that day
25 years of The Independent on Sunday: The stories, the writers and the changes over the last quarter of a century

25 years of The Independent on Sunday

The stories, the writers and the changes over the last quarter of a century
Homeless Veterans appeal: 'Really caring is a dangerous emotion in this kind of work'

Homeless Veterans appeal

As head of The Soldiers' Charity, Martin Rutledge has to temper compassion with realism. He tells Chris Green how his Army career prepared him
Wu-Tang Clan and The Sexual Objects offer fans a chance to own the only copies of their latest albums

Smash hit go under the hammer

It's nice to pick up a new record once in a while, but the purchasers of two latest releases can go a step further - by buying the only copy
Geeks who rocked the world: Documentary looks back at origins of the computer-games industry

The geeks who rocked the world

A new documentary looks back at origins of the computer-games industry
Belle & Sebastian interview: Stuart Murdoch reveals how the band is taking a new direction

Belle & Sebastian is taking a new direction

Twenty years ago, Belle & Sebastian was a fey indie band from Glasgow. It still is – except today, as prime mover Stuart Murdoch admits, it has a global cult following, from Hollywood to South Korea
America: Land of the free, home of the political dynasty

America: Land of the free, home of the political dynasty

These days in the US things are pretty much stuck where they are, both in politics and society at large, says Rupert Cornwell
A graphic history of US civil rights – in comic book form

A graphic history of US civil rights – in comic book form

A veteran of the Fifties campaigns is inspiring a new generation of activists
Winston Churchill: the enigma of a British hero

Winston Churchill: the enigma of a British hero

A C Benson called him 'a horrid little fellow', George Orwell would have shot him, but what a giant he seems now, says DJ Taylor
Growing mussels: Precious freshwater shellfish are thriving in a unique green project

Growing mussels

Precious freshwater shellfish are thriving in a unique green project