The phone outage that Bell Atlantic Corp. said would probably never happen again did yesterday in western Pennsylvania, where a computer problem similar to the one experienced here Wednesday caused a million people to lose phone service for most of the day.
"This is what I call a head-smacker. You hit your head, roll your eyes back, and the only thing that you know for sure is that it's unprecedented," said Larry Plumb, a Bell Atlantic spokesman in Arlington, Va.
At about the same time phone service hit the skids in Pennsylvania, engineers in California had to move quickly to fix an outage in the San Francisco Bay area. That outage, which lasted for about five minutes starting around 11 a.m., followed a similar outage in Los Angeles Wednesday, where phone service was knocked out for three hours due to a similar computer malfunction.
In all four cases, the problems were caused by malfunctions in the companies' "Signaling System 7," or SS7, networks, the sophisticated computer-run networks that sort and route calls.
In all instances, the hardware provider was DSC Communications Corp., of Plano, Texas, giving rise to new speculation about a possible computer software virus or universal programming glitch.
"We can't rule it out," said Anton J. Campanella, president of Bell Atlantic Corp. "We have been in touch with the FBI and nothing has been eliminated. But my own gut tells me we will find inside the switch a code problem that has suddenly surfaced for some reason."
A problem with switching software also was blamed for a similar outage in Greensboro, N.C., yesterday. Service was cut to about 45,000 downtown-area phone lines for 2 1/2 hours, Southern Bell officials said.
Yesterday's computer malfunction in Pennsylvania disrupted local phone service and some long-distance calls in Pennsylvania's 412 area code for about seven hours. Service, which went down about 11 a.m., was restored by 6 p.m.
Eric Rabe, a spokesman for Bell of Pennsylvania, a unit of Bell Atlantic, said engineers first noticed a problem in Pittsburgh about 11:04 a.m.
According to Mr. Rabe, a computer at a switching site began showing signs of an overload from "maintenance messages," which are messages the computer sends itself to confirm that its components are working properly. The problem was traced to a "signal transfer point (STP)," a supercomputer that sorts and routes calls.
That's the same problem that caused up to 5 million customers in Maryland, Washington, Virginia and parts of West Virginia to lose local phone service last week.
Engineers for Chesapeake & Potomac Telephone Co. have since traced the problem to a faulty circuit board in a Baltimore STP site, but they still don't know what caused the computer to overload itself with messages.
According to Mr. Rabe, engineers in Pennsylvania moved quickly to make sure there wasn't a repeat performance of what happened in C&P's territory last week.
He said technicians, after spotting the message buildup, shut down the system manually to prevent the problem from spreading.
"This was not like the problem in Washington and Baltimore," Mr. Rabe said. "When we saw the buildup of maintenance messages, we manually disabled it in an attempt to get the system to continue to operate."
Bell Atlantic has moved quickly to put in some quick fixes to mitigate the problem should it crop up again. But until the root cause of the problem is found, Mr. Campanella said deployment of SS7 technology throughout Bell Atlantic's territory will be slowed.
There are currently about six pairs of DSC-provided switches in use throughout Bell Atlantic's territory. Those switches route calls for almost 40 percent of Bell Atlantic's customer base, he said.
Since the first Bell Atlantic outage last week, a team of about 200 specialists have been working round-the-clock to find the cause of the outage.
Yesterday, Mr. Campanella said those ranks have been bolstered with telecommunications experts from American Telephone & Telegraph Co. and Northern Telecom, two major competitors of DSC.
Mr. Campanella said an answer to the software problem is expected within the week, but he wasn't offering any promises.
* The Associated Press contributed to this article.
The Chesapeake & Potomac Telephone Co. said last night that it would offer refunds to customers who used operators to place local calls Wednesday during the telephone outage.
The refunds will be offered to those whose bills reflect use of local operators on June 26.
The C&P rate for operator-assisted local calls is $1.55, according to an operator contacted last night. AT&T operators charged 80 cents to place local calls last week.
C&P made no mention of compensating businesses that suffered losses during the outage.