Groups for Inter Register Signaling

In R2 signaling, the forward and backward signals can have different meanings depending on which group is used. Three groups of forward signals and two groups of backward signals exist. The forward groups are I, II, and III, and the backward groups are A and B.

• Group I—These forward signals represent the called party number or dialed digits.

• Group II—These forward signals identify the calling party category.

• Group III—These forward signals represent the digits of the calling party number.

• Group A—These backward signals indicate if the signaling ended or if a particular forward signal is required.

• Group B—These backward signals are sent by the terminating switch to acknowledge a forward signal, or to provide call charging and called party information.

The following inter-register group sequence rules are used to identify the signal's group:

• The initial signal received by the incoming exchange is a Group I signal.

• Outgoing exchanges consider backward signals as Group A signals.

• Group A signals received by outgoing exchanges are used to identify whether the next signal is a Group B signal.

• Group B signals always indicate an end-of-signaling sequence. Feature Support

The end-to-end information and status that National R2 signaling provides enable support for several features. These features include free calls, called party hold, malicious call tracing, and release on failed connections.

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