
156 Chapter 5 • Using ISDN and DDR to Enhance Remote Access Connectivity
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TE1 Terminal Equipment 1 is a device that is compatible with
ISDN, such as a digital telephone or a router with an ISDN inter-
face.
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NT2 The Network Termination 2 device directs traffic to and from
the user devices and the NT1, such as a private branch exchange
(PBX).
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NT1 The Network Termination 1 device connects the ISDN wiring
(four-wire ISDN wiring) to the conventional local loop (two-wire
standard wiring).
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LE The Local Exchange is the ISDN switch residing in the CO.
The reference points from Figure 5.2 are:
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R (Rate) Reference point between TA and non-ISDN device.
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S (System) ...