Did telephone company executives choose to sacrifice the reliability of basic phone service, even to a small degree, for the prospect of money-making products such as Caller ID? And have they skimped on spending for backup systems now that they are no longer regulated as closely?
Some people in the telecommunications industry are beginning to ask these questions of local phone companies in the wake of the four extraordinary phone outages that affected millions of customers in the last week.
And regardless of how much the local phone companies knew about the risks of the new switching system, customers are being warned that such outages could become common.
"I think you're going to expect a lot more of this happening, not because of the hardware and software, but deregulation of the local exchange carriers," said Phil Freedenburg of Federal Engineering Inc., an independent telecommunications consulting firm in Fairfax, Va.
Mr. Freedenburg and others suggested that when the local phone companies were allowed the freedom of charging what they wanted for some services -- those deemed more competitive than basic phone service -- they opted not to invest as heavily as they might have in the backups that would keep the system as reliable as it had been in the past.
"What amazes me is that C&P; doesn't have the capability to have some redundancies built in to check on each other," said Ted Theodosios, president of Integrated Systems Planning Inc., a telecommunications consulting firm in Towson.
Such redundancies might have raised an electronic red flag that aproblem was developing at the Chesapeake & Potomac Telephone Co.'s Baltimore switching point. C&P; now believes that a problem at the switching point caused the glitch that led to Wednesday's outage.
Telecommunications industry experts are also raising concerns about the electronic signaling system that many phone companies across the country, including C&P;, have installed during the last six years.
The new system, called Signaling System 7, has allowed C&P; to sell products such as Caller ID, which identifies for customers the phone number of the incoming caller, and variable call forwarding, by which customers can program numbers where their calls can be forwarded.
The SS7 technology also has reduced dramatically the phone company's costs, the amount of telephone fraud, and the amount of time it takes to make most calls, according to C&P; spokesman Al Burman.
But with those efficiencies and enhancements have come risks that observers have warned of for years. In fact, the nationwide telephone "brownout" in January 1990 resulted from a software glitch that occurred soon after the American Telephone & Telegraph Co. started up its new SS7 system.
SS7 is a generic term for a signaling system that uses two distinct lines per phone call. Under the old "in-band" system, the line that carried the caller's voice also had the intelligence to seek out a route and test to see if the recipient's line was busy.
The new "out-of-band" system uses a separate electronic path to seek out the route and test the line, a much faster process than tying up a voice line for every dialing attempt, successful or not. ,, That dual system also has allowed the combined voice and data services, such as Caller ID.
But by making the basic person-to-person phone call dependent on a separate line, and on the complex computer software that supports the whole system, the phone companies introduced an element of risk to which basic phone users never had been exposed before.
That exposure led to the snowball effect that spread Wednesday's glitch from the Baltimore switching point to a number of others in Washington, Virginia and portions of West Virginia.
"There was always the basic assumption that the technological changes would not affect the basic phone service," said John Glynn, who heads the Office of the People's Counsel, a state agency that represents consumers in utility rate cases. "Maybe today we have to think about it differently," he said.
When they opted for the enhanced SS7 system, the phone companies had to weigh that risk against the potential for higher revenues from the new services. Mr. Burman of C&P; says the risk was minimal compared to the benefits for most phone users.
"Based upon the fact that it did provide many improvements to consumers, many not even on the market yet," Mr. Burman said the company believes it made the right choice. After all, he said, AT&T; had been using a "common channel" signaling system like the SS7 since the late 1970s. And if the problem turns out to be simply a faulty circuit board, he said, there's no reason to believe the outages that hit Pittsburgh, Los Angeles, San Francisco and the mid-Atlantic states will continue.
Mr. Freedenburg is less optimistic. "There's a fundamental flaw in the architecture of the whole system," he said. "A failure in one location is no longer contained."
Phone outages linked to SS7
Six recent telephone outages have been linked to Signaling System No. 7 (SS7), a switching system introduced in 1985 that routes telephone calls. AT&T;'s failure in 1990 occurred with an SS7 system made by AT&T; itself. Four of the other five failures (noted with **) occurred in SS7 equipment made by DSC Corp. of Plano, Texas.
.. .. .. .. .. .. .. Telephone .. .. .. .. .. .. .. .. Suspected
Date .. .. .. .. .. .. company .. .. Region .. .. ... .. .. cause
Jan. 15, 1990 .. .. . AT&T..; .. Nationwide .. .. .. ..S7 software
June 26, 1991 .. .. . C&P; * ..Md., Va., D.C., .. ..S7 software **
.. .. .. .. .. .. .. .. .. .. .parts of West Va.
June 26, 1991 .. .. . Pacific .. ..Southern .. . ..SS7 system **
.. .. .. .. .. .. .. Bell .. .. .California
July 1, 1991 .. .. ...Bell of .. Pittsburgh .. ..SS7 software **
.. .. .. .. .. .. .. Pa*
BJuly 1, 1991 .. .. .. Pacific .. .. .. San .. .. SS7 software **
.. .. .. .. .. .. .. .Telesis .. .. Franciso area
July 1, 1991 .. .. .. Southern .. ..Greensboro, .. .. Undetermined
.. .. .. .. .. .. .. .Bell .. .. .. N.C.
* Part of Bell Atlantic