When the Main Street Cos., a 125-employee restaurant and catering company in Princeton, N.J., wanted to link the local area computer networks of its three sites, vice-president John Marshall considered several options for the $4-million business. Marshall had read about ISDN technology in a computer magazine, and he contacted Bell Atlantic about the service.

At first, Marshall recalls, he had no luck. But in 1994 Bell Atlantic began to promote ISDN more aggressively, and Marshall signed up. Today he is happy to report that Bell Atlantic provides him with ISDN lines that link the company's two restaurant/coffeehouses to its production facility -- at a much lower cost than the other available wide-area-networking options. Marshall estimates that the next-cheapest alternative would have cost Main Street $800 to $1,000 a month, plus initial hardware outlays of some $15,000. For his ISDN service, Marshall pays $80 a month after a hardware investment of $3,600. He says the ISDN was easy to install and involved two big changes: one was adding to each server an ISDN card from Digi International, in Eden Prairie, Minn. ("You just plop it in like a modem," Marshall says.) The other was buying for each building a device called an NT1, the box that enables a company to hook into the ISDN. Marshall bought his NT1's from Tone Commander Systems, in Mukilteo, Wash. With the new companywide network, Main Street's three sites can easily share databases, information, and staff expertise.