Pacific Bell Blaze Points Up Some High-Tech Flaws : Telecommunications: While new technology is improving the phone system overall, it also raises the stakes when problems occur.

While new technology is helping to improve the overall reliability of the nation’s phone system, it can also lead to bigger problems when something goes wrong.

That was one of the troubling conclusions raised by telecommunications experts on Wednesday in the wake of Tuesday’s fire at Pacific Bell’s Bunker Hill facility in Los Angeles, which resulted in blocked calls and disrupted business throughout the city.

In the annals of telecommunications blackouts, the Pacific Bell disaster was something of an anomaly. The majority of disruptions are caused by phone lines being physically damaged or dug up and by problems with new computer software installed in the networks without first working out the bugs.

Tuesday’s disruption was caused by a fire that damaged power lines in the 17-story building, leading to a major failure of a critical switch that served as the hub for millions of calls. The fire burned an area only about 50 square feet.

While the concept of a telephone switching network hasn’t changed much since the days when women operators on roller skates manually switched the circuits to route calls, the replacement of copper wires and analog switches with fiber-optic cables and digital switches has made for faster and more flexible systems.

For example, in the newer “intelligent” fiber networks--which Pacific Bell has begun to install--the network can sense a break in the cable and instantly redirect calls to alternative switches.

Telecommunications experts and regulatory officials said that new rules and rapidly improving technology has led to a decrease in the number of major service disruptions nationwide over the last year.

“There is good evidence now that we’re better than we were a year ago,” said Paul Henson, who heads a telephone network watchdog group appointed by the Federal Communications Commission in late 1992 after a series of serious outages disrupted service to millions of telephone users.

*

Last year, Henson’s group recorded a total of 167 outages, each affecting more than 30,000 customers for more than 30 minutes. During the last three months of the year, phone companies reported 28 outages--significantly fewer than in the previous reporting periods.

Henson said Pacific Bell, which reported 13 outages in 1993, one less than the previous year, had one of the best reliability records of the local phone companies. This year, Pacific Bell has had two outages--Tuesday’s and one resulting from January’s Northridge earthquake.

But while the new technology has reduced outages, the disruptions that do occur can be more pronounced. For example, fiber cables can can carry thousands of times more data than copper wires. But since the traffic is concentrated in fewer pipelines, a damaged cable means a higher percentage of calls are disrupted.

In addition, as the phone companies depend increasingly on computers to run their systems, they face the specter of software problems that are often difficult to pinpoint.

“There’s stuff that happens in the physical network and there’s stuff that happens in cyberspace, and the stuff in cyberspace can be really, really hard to fix,” said Denise Caruso, a San Francisco-based telecommunications analyst.

Another problem is that officials are required by law to install sprinklers in high-rise buildings. But the use of water to extinguish fires on sensitive machines may cause more problems than it solves.

The potential for problems could increase as regulators move toward allowing cable firms and long-distance carriers to compete against the local phone companies.

“We may be entering an era in which reliability declines in the local market as competition based on cost intensifies,” said Ryan James, director of the Boston-based Yankee Telecommunications Group, a consulting firm. “Fortunately, technology has a way of coming back to save us.”

For their part, Pacific Bell officials said they hoped their evaluation of Tuesday’s fire will reduce the chances of future catastrophes.

“We plan for various contingencies and this time we were caught without either primary or secondary power,” said Bill Chubb, regional manager for Pacific Bell. “But it’s premature to say the design is bad, before we understand exactly what happened.”

John Seazholtz, vice president for technology at regional phone company Bell Atlantic, had his engineers reviewing power installation and maintenance procedures Wednesday morning after being briefed on the Pacific Bell disaster.

“We’re reviewing our power jobs, looking at what precautions vendors are taking, what training they have, whether additional criteria (should) be established,” Seazholtz said.

Times staff writer John Mitchell contributed to this report.