Electronic smog - `invisible assassin'

IT IS the invisible assassin of computer networks and its latest victims are thousands of travellers on the London Underground, where trains have been delayed by signalling failures.

Electronic "smog" - interference caused by the growth of electrical gadgets such as mobile phones and pagers - is creating havoc with computer-controlled signals being installed on the Central Line.

London Underground admitted yesterday that the phenomenon is hitting its attempt to introduce the state-of-the-art signalling system. The computers have shut down as a fail-safe precaution when communications between the trains and the track have become confused due to the electronic interference caused by external power sources.

A spokesman said that the company intends to install shielding equipment to prevent the electronic smog from creating further problems.

"To an extent the problem has affected all stations on the line but not always to the point that it creates a system failure. We don't care where it comes from, we just want to find a solution and to stop the interference,'' he said.

Power cables on the Underground are thought to be primarily responsible for generating the electromagnetic disturbances that have affected the signalling computers. But laptops, mobile phones and other devices are believed to be making matters worse, the spokesman said.

Electronic smog has been a growing problem because of the inclusion of sophisticated microelectronic circuitry in everything from cars and washing machines to phones and cameras.

Edward Leigh, when he was trade and industry minister in 1993, cited instances of electronic smog causing fatal accidents - a British worker died when a computer-controlled crane dropped its load; robots killed two Japanese workers when the machines ran out of control; and anti-lock brakes would suddenly came into operation on a section of German motorway that ran past a powerful radio transmitter.

Mobile phones have been blamed for interfering with hospital life-support systems and were even credited with disrupting the computers controlling the moving stage sets for Sunset Boulevard, the Andrew Lloyd Webber musical.

Airlines warn passengers to switch off mobile phones and laptops at critical stages in the flight because of interference to sensitive navigation computers.

A European-wide directive came into effect in 1996 to curb unwanted emissions of electromagnetic waves from electrical devices. But some experts believe it is failing to stem the growth of electronic pollution.

The best method of shielding equipment against electronic smog is to build a device called a Faraday cage around the equipment, which the military has done for years to protect its command and control systems from electronic jamming. This, however, is cumbersome and too expensive for most civilian computers.