ISDN Line Ordering and ConfigurationCSX400 and CSX400-DC User’s Guide 25In the U.S. and Canada, Network Terminator equipment (NT1) is required to provide an interfacebetween the CSX400 and the ISDN line. The NT1 offers conversion between the two-wire twistedpair (U-loop interface) used by telephone companies and the four-wire terminal equipment (S/TInterface) as well as line-testing capabilities. External Network Terminator equipment comes witha power supply (built-in or external).In Europe and Japan, the telephone company provides the NT1 and offers end-users the S/Tinterface. The S refers to a connection between customer equipment in some ISDN configurationswhen a PBX is present. The T refers to the connection between the NT1 device and the CSX400.The ISDN pairs are the same wires that exist for analog telephone service. In most cases, the samewires can be used for the ISDN line. The EIA/TIA standard for wiring is Unshielded Twisted Pair(UTP) cable, Category 3 or above, 24 AWG (American Wire Gauge). The standard alsorecommends using 8-position RJ45 jacks for new ISDN service installation. No specialconditioning is required; in some cases, conditioning must be removed.ISDN BRI ConfigurationsISDN BRI lines can be configured in point-to-point and multi-point configurations. With apoint-to-point configuration, only one device is connected to the ISDN line. With a multi-pointconfiguration, it is possible to have up to 8 devices (telephones, faxes, routers, etc.) connected tothe line.Since the ISDN BRI line is used for a high speed LAN-to-LAN link, you must ensure thatadditional devices connected to the S/T interface allow sufficient access for the bandwidthrequirements of the CSX400.SPIDs, Directory Numbers and Telephone NumbersThe service provider gives you up to three sets of numbers for identifying the ISDN line anddevices. You may be assigned none, one or two Service Profile Identifier numbers (SPIDs) orDirectory Numbers (DNs) depending on the service provider and country.Phone NumbersNumbers used for others to dial into the ISDN B channels on your ISDN line (similar to analogline phone numbers).Directory NumbersAddress assigned by the ISDN service provider for each device operating on the line. This numbercan be similar to the phone number. The Directory Number is not generally implemented outsidethe U.S.
