Callers in Chicago suburbs start to get dial tones again. Fire shows vulnerability of high-tech nerve centers

The great Chicago telephone snarl is coming to a close. By Monday, almost all of the 35,000 phoneless residents and businesses in the city's west and southwest suburbs had regained at least limited service.

Hundreds of thousands of other Chicago-area telephone customers, who partially lost service, also found ways to cope - sometimes through unusual and circuitous means.

The two-week-long mess demonstrated the flipsides of the new communications technology. As it gets more sophisticated, it is increasingly dependent upon fewer and larger switching stations, telephone company officials say. On the other hand, it allows tremendous flexibility in getting around the problem.

``When you have advancing technology, you tend to have more concentration,'' says one technical executive for an independent telephone company. Ten years ago, a central office might contain 20,000 to 30,000 lines; today, 60,000 to 85,000 is common, he adds. But ``the new technology systems are so flexible.'' It allows telephone companies to fix or replace equipment rapidly.

This weekend, for example, some 400,000 North Carolina telephone users lost partial or full service after circuits failed at a high-volume central office in Charlotte, N.C. But the failure Saturday afternoon was mostly back in service early Sunday morning, says Southern Bell spokeswoman Amy Giles.

The Illinois Bell disaster is more profound because of the extent and location of the damage. On Sunday, May 8, a fire knocked out the telephone switching station in the suburb of Hinsdale, Ill. The station not only served 35,000 customers, it also was the gateway through which regional and long-distance calls were routed for 30 other central stations.

Thus, when the station was hit, a wide swath of western and southwestern Chicago suburbs could not make suburb-to-suburb or long-distance calls. Illinois Bell technicians scrambled to repair the damaged lines and prepare for new switching equipment, but many residents and businesses couldn't call out or be reached outside their local communities.

``That situation has improved greatly'' over the weekend, Illinois Bell spokesman Larry Cose said yesterday. But by midmorning it was still impossible to reach some residents long-distance. The company plans to install new switching equipment for half the customers by late Thursday.

The overall impact of the loss of service is still not known.

Residents got around the phone problems by relaying messages through friends or using one of the emergency phone centers that Illinois Bell set up in several towns.

``It has been hard on everybody,'' says Juli Hand, a part-time word processor from Glen Ellyn, Ill., who lost her long-distance service. Some 35,000 residents had, at best, only intermittent service for nearly two weeks.

But the biggest burden fell on business. Newspapers chronicled the mounting problems of some establishments - such as travel agencies and telemarketing companies - which were so dependent on the phone that they simply closed down a few days. One pizza delivery company in suburban Westmont used a mobile cellular phone to keep in touch with suppliers but lost most of its customers. The solution: park its 12 delivery trucks in the busiest areas and have them radio in orders.

When one suburban sales office of a major Chicago-area wholesaler was unable to make long-distance calls, the company set up the salesmen in the cafeteria of the home office. By adjusting its own phone-switching equipment, the salesmen made outgoing calls and had their own telephone numbers operative.