ast as analog POTS is filtering. The PSTN uses filters to keep unwanted frequencies out of the 4 kHz analog voice pass band. Digital signals are not impeded by spurious frequencies, SO the same twisted pair cable can, using digital modulation techniques, deliver much greater throughput. Speed, reliability, and lack of an alternative account for ISDN BRI's popularity. Approximately one million ISDN BRI lines existed at year-end 1995. This represents a 300% increase from the preceding year. It is estimated that, in 1996, this number more than doubled to 2.5 million. Although video communication applications accounted for only a small portion of the installations (5-10%) ISDN BRI suits interactive streaming media applications. ISDN BRI service charges vary greatly, both within the United States and abroad. Rates fluctuate not only due to tariff differences, but also in relation to the distance between the customer and central office. On average, ISDN lines are priced about 1.5 to 2 times higher than POTS lines. ISDN service has many advantages over POTS. ISDN data connections are set up in less than a second compared with over 30 seconds for POTS connections. ISDN can also be configured to provide enhanced Caller ID and other custom network features. There are many B and D channel configuration choices (although choices narrow when videoconferencing is passed over the B channel). ISDN BRI can terminate up to 18,000 feet from a CO (in some areas, 24,000 feet), without signal reinforcement. COs have to be equipped for ISDN; if they do not have this capability, or if the customer is too far away from the CO, a telephone company may be able to provide ISDN BRI through the use of a Basic Rate Interface Terminal Extender (BRITE) card. BRITE technology uses T-1 carrier to transport up to 24 ISDN BRI channels. Since each BRI has three channels-two B and one D-this means that a BRITE card can support eight total ISDN BRI connections. Video Communications: The Whole Picture The ISDN NT-1 Eventually, ISDN BRI ends up at the cu