A Simple Answer : Unsophisticated Computer Part Failed, Causing Crash of Complex 911 System

It’s one of the biggest, most complex and expensive systems of its kind.

But as Los Angeles Police Department officials learned on Saturday, the highly sophisticated 911 emergency telephone system depends on a lot of ordinary computer parts.

They can--and do--break.

As technicians scrambled to get Los Angeles’ emergency lines reopened Saturday during a four-hour collapse, it slowly became clear that the afternoon crash was caused by a simple computer board--similar in appearance to the plates found in the back of televisions or home computers--that failed for still unknown reasons, officials said Monday.

The so-called SL/1 positron switch’s malfunction shut down about half the Police Department’s 911 system and, during the worst moments Saturday afternoon, more than 70% of calls to the emergency lines were rejected, according to Capt. Forrest Lewallen of the police communications division.

The system collapsed about 1 p.m. and was not fully functional until 5:15 p.m., officials said. Police said they were not aware of any emergency that went unanswered. Callers were still able to dial local police directly.

Despite the planning that went into the city’s 5-year-old 911 system and its myriad precautionary and back-up systems, “failure of the switch is something we had not anticipated,” Lewallen said.

The board that broke Saturday is a power conversion board that helps control power fed to a complex switching system. The switch receives incoming 911 calls and routes them virtually instantaneously to the first open phone line.

Officials at Pacific Bell, which engineered the system and owns the equipment that failed Saturday, also could not immediately explain what went wrong.

“It is extremely rare” for the simple power converter computer board to fail, said Mike Fink, Pacific Bell service manager. The problem parts have been shipped to a Pacific Bell laboratory, where they are being examined by technicians in search of an answer.

“It’s an off-the-shelf part” that involves a low degree of technology and sells for $1,000, Fink said.

Fink said the board that failed is usually so reliable and simple that no backup was designed into the system. It’s virtually the only part of the system--which cost $1.6 million to install--without a backup.

A spokesman for Pacific Bell, which manages several hundred 911 systems across the state, said the company has experienced only one other failure in the last year.

Officials at General Telephone, which manages 98 emergency telephone systems statewide, said that company has had only one failure in the last two years.

None of the other failures was linked to the part that malfunctioned Saturday.

Emergency System

The last such failure to occur in the Los Angeles system was on Feb. 16, 1987, when the emergency system blacked out for an hour because of a power failure.

The city’s vast system suffered quite a few problems, however, when it was installed in 1984.

Based on experiences in other California cities, city officials had anticipated that during a gearing-up period, only 30% to 40% of emergency callers would dial 911 rather than call authorities on other numbers. Yet within a year, the call level reached 50%, and it now stands at 73%.

The original equipment developed by American Telephone & Telegraph proved inadequate to handle the volume of calls.

The city’s system proved so slow that during peak times--such as during the 1985 Night Stalker series of crimes--callers had to wait 30 seconds or more for an operator. That compared to a wait of under three seconds in most other locales.

At this point, officials say, the technological problems have been overcome and calls are normally answered within three seconds during normal hours and 10 seconds during peak periods.

More often, the biggest problem with the system is callers misusing the 911 service, officials say. Los Angeles police say that up to 75% of the average 5,500 calls received daily prove to be non-emergencies.

Authorities say the attention paid to problems in the 911 network serve only to dramatize the overall value of the service, which is often credited for saving lives.

Such success stories have ranged from emergency calls by 5-year olds to one from a man who was bound by his assailants and managed to dial 911 with his tongue.