Figure 97 ISDN Network Components

RR1 4-wire

Teico 2-wire

riTi

TA typically incîude& NT1

XM PU

riTi

TA typically incîude& NT1

Terminal equipment includes the following:

• TE1— Native ISDN terminal, such as a router or telephone

• TE2— N on-native ISDN termin al, such as a router or PC; needs a terminal adapter (TA) Netw ork termin ation devices include the following:

• NT1— CPE in North Am erica; earrieo provid ed elsewh ere. It is the (device re sponsi ble for the t division mu l tiplexmg (TDM) between the four-wire connection from the router to the two-wire connection to the telco. The NT1 applies power to the line.

• NT2— Typically found in private branch exchanges (PBXs). There is an NT1/2 available to pro function of °oth hhe NT1 and NT2. Not always used.

A line termination (LT) is a physical connection to an ISDN switch, whereas reference points are m conceptual int:etfaces. "l"!^ am j ast lettero of1 mhe alphabet that dnn' t stmd for anything, but they c to go in alphabetic order toward the semce provider: rc S, T, U . °ictures are quite helpful here, ar concepts appear to be pretty significant on all Cisco exams. Figure 9-8 gives you a block diagram r the ISDN functions and the following reference points:

• U— Between NT1 and the carrier network

• V— Betwepn ISDN swi tches within the carrien cloud

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