3Com NETBuilder SI, SuperStack II manual NT1s and Power Supplies

NT1s and Power Supplies 193

■The SPID numbers must be unique. The 2-digit TID can be any number from 0 to 62. The TID has no effect on the operation of the SuperStack II bridge/router, but it is a necessary part of the SPID that the bridge/router uses to gain access to the ISDN network.

■If you request ISDN service from a Northern Telecom DMS-100 service provider, the format is:

Area code + 7-digit telephone number + 0 to 8 digit suffix + 2 digit TID.

■The TID can be any number from 0 to 62, but needs to be unique so that the SPIDs are also unique. This format applies when the switch is running Custom and NI-1 (North American 3) versions of software.

■If you order AT&T 5ESS Custom ISDN services, choose either a Type A or Type E terminal. The Type E terminal is preferable because it is for data only.

■Do not request supplementary services, such as autohold or conference, because a SuperStack II bridge/router does not support them.

NT1s and Power The models 43x and 53x bridge/routers do not come with an NT1. North

SuppliesAmerican telephone companies require an NT1 and a power supply for every ISDN line. Your service provider or telephone company can provide you with an NT1 and power supply for a small monthly fee. However, you may prefer to purchase it from an ISDN equipment vendor. The NT1 and power supply may come in a single, standalone box or the two may be in separate units. In this discussion, the two units together are referred to as an NT1.

The model 44x and model 54x bridge/routers have an integrated NT1.

Telephone companies in North America use two kinds of NT1s, differentiated by the data encoding scheme used in transmitting data between the NT1 and the telephone company’s equipment. The two data encoding schemes are 2B1Q (two bits mapped into one quaternary symbol) and alternate mark inversion (AMI). The 2B1Q scheme is the dominant method in use today. The AMI scheme is older and rarely used.