A computer malfunction in the local phone network left as many as 5 million people in Maryland, Washington, Virginia and parts of West Virginia without phone service yesterday, the worst outage in memory at Chesapeake & Potomac Telephone Co.
The malfunction, first detected about noon yesterday, affected 2 million business and residential customers in Maryland alone, said Jeanine Smetana, a C&P; spokeswoman.
Across the region, people weren't able to place local calls, and placing long-distance calls within the area was hit-or-miss at best.
By 7:30 last night, most of the local network was back up and running as normal. By 9:30, the system had been fully restored.
"We've taken it off the critical list. Let's just say it's in a 'guarded condition,' " said Jay Grossman, a spokesman for Bell Atlantic Corp., the corporate parent of C&P.; "We will continue to watch it closely throughout the evening."
According to Larry Plumb, a Bell Atlantic spokesman in Alexandria, Va., the outage stemmed from a malfunction in four computerized transfer points that route and sort calls. Known as "Signaling System 7," or SS7, these state-of-the-art switches act as the electronic "brains" of C&P;'s local network. As central transfer points, SS7 switches set up and route calls among hundreds of computerized switches in the region.
Because the master SS7 switches failed yesterday, so did the network: At the height of the outage, 606 of 681 switches that rely on the four SS7 transfer sites for routing information were down.
The problem first surfaced in a signal transfer point in Baltimore, but the origin of the systemwide breakdown had not been pinned down as of early this morning.
Edward Stanley, a C&P; spokesman in Washington, said that the likely culprit was a programming error in the SS7 system.
That's the same problem that wreaked havoc with AT&T;'s long-distance network in January 1990. A programming bug left customers nationwide unable to place long-distance calls for the better part of a business day.
To make up for the inconvenience, AT&T; offered a day of discount calling the next month, on Valentine's Day.
Bell Atlantic's Mr. Grossman said he didn't know whether Bell Atlantic could offer the same sweetheart deal to its customers because of state regulatory restrictions.
"We can't give money back without regulatory approval, but we are looking at that option," he said.
C&P;'s computerized failure left millions of customers unable to place local phone calls outside their immediate neighborhoods. Some people resorted to using their long-distance calling cards to make local calls.
When the volume of calls began to build in the afternoon as a result of the crush of frustrated callers trying to get through, cellular communications and long-distance lines also became jammed.
All the while, the ringing phones of Baltimore's businesses -- the lifelines of many ventures -- were silenced. That forced some of those with a critical need to turn to more creative means to communicate.
Charles "Chuck" Thompson, a copywriter with W. B. Doner Co., the Baltimore-based advertising and public relations firm, said the outage forced him to take to the streets -- literally -- to wrap up a television commercial for Baltimore Ford dealers.
Because the ad was scheduled to run last night, Mr. Thompson said, he had to hustle the four blocks between the recording studio and his office every time he had to get an approval on the tape from officials at Doner.
Maryland's phone outage
Who was affected: Up to 6.3 million of C&P; Telephone's 7.1 million telephone lines, or about 5 million residential and business customers, in Maryland, the District of Columbia, Northern Virginia and West Virginia. Problems with four master signaling switches in the affected area disabled 606 out of 681 "dumb" switches.
Ways to place calls: AT&T; long-distance operators yesterday were placing local calls for customers at a cost of 80 cents per call. The AT&T; operator can be reached by dialing "00." Customers using calling cards reported success yesterday in placing calls.
How long did the problem last?: The system had been fully restored by 9:30 last night, C&P; said, but as of early this morning the origin of the problem had not been pinned down.
Possibility of a refund: A spokesman said he had "no idea" whether customers would receive refunds because of the outage.