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Figure 15 shows, for a generic integrated trunk-side BRI, the ISDN Interface Reference Points. Table 144 gives definitions for the generic ISDN Interface Reference Points.
Figure 15. Integrated Trunk-Side BRI, ISDN Interface Reference Points
| LT |
Logical Terminal |
| V |
Primary Rate user/network (asymmetrical) trunk interface. The ECS is capable of acting as the user or as the network side of this 1.544 - or 2.048-Mbps interface. |
| R |
Interface between Terminal Equipment and Network Termination |
| S |
Basic Rate network-side 4-wire line interface |
| S/T |
4-wire Basic Rate connection to a Network Termination1. |
| T |
4-wire Basic Rate interface to a Network Termination.2 |
| TE |
Terminal Equipment |
| U |
Basic Rate network-side 2-wire line interface. |
| 1 |
TN556B ISDN-BRI 4-Wire S/T-NT Line (A-law) |
| 2 |
TN 2185 ISDN-BRI 4-Wire S Interface (Trunk Side) |
| 3 |
TN2198 ISDN-BRI 2-Wire U Interface |
| 4 |
TN2198 ISDN-BRI 2-Wire U Interface |
| 5 |
TN 2185 ISDN-BRI 4-Wire S Interface (Trunk Side) |
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1Network Termination 2 (NT2), that terminates Layer 1 and higher layers. PBXs, LANs, and terminal controllers typically provide NT2 functionality including protocol handling and multiplexing for Layers 2 and 3.
2Network Termination 1 (NT1), that terminates Layer 1 and monitors maintenance, performance, timing, power transfer, multiplexing, and multi-drop termination with contention resolution.
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