A set of reference points are defined in the ISDN standard to refer to certain points between the telco and the end user ISDN equipment.
- R - defines the point between a non-ISDN device and a terminal adapter (TA) which provides translation to and from such a device
- S - defines the point between the ISDN equipment (or TA) and a Network Termination Type 2 (NT-2) device
- T - defines the point between the NT-2 and NT-1 devices1
1 Most NT-1 devices can perform the functions of the NT-2 as well, and so the S and T reference points are generally collapsed into the S/T reference point.
² Inside North America, the NT-1 device is considered customer premises equipment (CPE) and must be maintained by the customer, thus, the U interface is provided to the customer. In other locations, the NT-1 device is maintained by the telco, and the S/T interface is provided to the customer. In India, service providers provide U interface and an NT1 may be supplied by Service provider as part of service offering
Read more about this topic: Integrated Services Digital Network
Famous quotes containing the words reference and/or points:
“In sum, all actions and habits are to be esteemed good or evil by their causes and usefulness in reference to the commonwealth, and not by their mediocrity, nor by their being commended. For several men praise several customs, and, contrarily, what one calls vice, another calls virtue, as their present affections lead them.”
—Thomas Hobbes (1579–1688)
“In writing biography, fact and fiction shouldn’t be mixed. And if they are, the fictional points should be printed in red ink, the facts printed in black ink.”
—Catherine Drinker Bowen (1897–1973)