stomer's premises as a single twisted pair. These two wires terminate on a building block or protector and are then connected to an NT-1 (network termination, type one, device). As originally conceived by the CCITT, the NT is service-provider-owned equipment installed on the customer's premises. It establishes the point of telecommunications service delivery by a carrier. In the U.S. only, provision of the NT is the customer's responsibility (as mandated by the FCC's Network Channel Termination Equipment Order). On one side of the NT- 1, circuit integrity is the responsibility of the carrier. On the other side, it is the responsibility of the customer. As such, the NT-1 is just like any other network demarcation (demarc) point. The NT-1 is about the size of a stand-alone modem and requires a power supply. The power supply plugs into a commercial power outlet in the customer's equipment room. This is a drawback of ISDN compared to POTS. POTS is powered by batteries in the CO. ISDN BRI requires more power than can be provided over the local loop. If an ISDN BRI-supported videoconferencing system must remain operational even during times of commercial power failure, a customer must provide a battery or uninterruptible power supply. NT1 units allow up to eight different devices to be daisy-chained to the ISDN circuit, and thereby enable all eight to use it simultaneously or to contend for the circuit. Thus, as many as eight videoconferencing devices could share the same ISDN BRI line and contend with one other for the B channels as needed. NT-1s and their associated power supplies vary widely in price; the cost difference correlates to capability. More expensive NT-1s can terminate ISDN offered by both AT&T and Northern Telecom. The cheaper ones are of switch-specific design. Some equipment vendors build the NTI-1 into CPE. The disadvantage to a built-in NT-1 is that it cannot be shared by other systems. Domestic Regional Office-Chicago Phone Phone Corporate Headquarters-New York T1/PR Router SW384=384K Pacific Rim H