DSC Communications Corp., the manufacturer of telephone equipment that has been linked to five phone outages in the past week, yesterday began making available software programming patches to its customers as a preventive measure.
Terry Adams, a spokesman for Plano, Texas-based DSC, said the company was making available to all of its customers -- not just those who have experienced outages over the last week -- "interim" software to use until the root cause of the widespread outages can be identified.
"We have modified the equipment to adjust to what we perceive to be network conditions today," Mr. Adams said. "We are making them available to everyone."
The equipment in question is DSC's "signal transfer points," or STPs, which are basically supercomputers that sort and route telephone calls across a network. STPs are a critical part of the "Signaling System 7," or SS7, networks used today by the regional Bell telephone companies.
DSC has sold 100 STPs to date, most of them domestically, Mr. Adams said. Current DSC customers include MCI Communications Corp., US Sprint and GTE Corp.
Mr. Adams declined to say how many customers have asked for the programming patch, which is basically a rewrite of a portion of software.
"Some have and some haven't," asked for the patch, he said.
SS7 systems, used by all the Bell phone companies and most major long-distance companies today, use a sophisticated network of electronic switches and computers to sort and route calls quickly and efficiently. The intelligence built into these systems allows companies to offer such services as Caller ID and Call Waiting, and they help cut down on toll fraud.
But the downside to using such sophisticated systems, which defy easy fixes in the event of a break down, has been visible this past week.
On June 26, local phone service in Baltimore, Washington, Virginia and parts of West Virginia was disrupted because of a failure in an STP in Baltimore. The outage left up to 5 million customers of Chesapeake & Potomac Telephone Co. without phone service for most of the day.
That same day, a similar outage was reported in Los Angeles for more than three hours.
Then, on Monday, outages were reported in the areas surrounding Pittsburgh and San Francisco. The California disruption lasted for only a few minutes, but the Pittsburgh outage, which affected a million people in the 412 area code, lasted for most of the day.
Scattered problems with placing local calls were still being reported yesterday in the Pittsburgh area. Those problems, which affected up to 300,000 people, were largely cleared up by midafternoon, according to Bell of Pennsylvania.
In all cases, a failure in an STP signaling station provided by DSC was the suspected culprit.
Bell Atlantic Corp., the parent company of both C&P; and Bell of Pennsylvania, has launched what amounts to a technological manhunt for the cause of the unprecedented outages. But after a week of exhaustive research by more than 200 telecommunications engineers, the cause has not yet been found.
With the installation of the latest programming patch, Bell Atlantic officials yesterday were saying the persistent outage problem, for now, should be mitigated. But they weren't offering any promises.
"The software obviously has a major problem," John Seazholtz, vice president technology and information services for Bell Atlantic phone companies, said yesterday at a technical briefing. "The manufacturer says this [programming patch] will clear it up. We'll see."