ISDN Protocol Administrator's and Developer's Guide ... - Intervoice

ISDN OverviewISDN Reference PointsReference points define the points of communication between systemcomponents. Different protocols may be used on either side of the point.The points are defined in Table 1-2.Table 1-2. ISDN Reference PointsPointCQRSTUDescriptionA reference point specific to QSIG where the physical connectionto PINXs is made.A reference point specific to QSIG that is the logical signalingpoint between two PINXs.A reference point for communication between a terminal adapter(TA) and non-ISDN compatible terminal equipment (TE).A reference link between the TA or TE and the network terminationequipment.A communication reference point between a Local LoopTerminator and the user switching equipment.A communication reference point between the network terminationequipment and the local exchange. The U reference point may becalled a “network boundary.”ISDN CodesetsCodesets are a method of changing the meanings of informationelements for private use. Codeset definitions are specific to particularservice providers.The same value mayhave different meaningsin various codesets. Mostelements usually appearonly once in each frame.Three main codesets are defined in Q.931. In each codeset, a section ofthe information elements are defined by the associated variant of theprotocol60001262, First Edition Overview 1-3