Dialogic 6.2 manual November 340

CPE Signaling Model

Information passed from the inbound side to the outbound side is:

„Called line condition (for example, free with change, busy, etc.)

„Network congestion

ITU recommendations specify a set of 6 frequencies to be used for forward signals, and another 6 for backward signals. Each signal consists of 2 frequencies, thus providing 15 forward signals and

15 backward signals. The recommendations allow countries to use only 5 frequencies (10 signals) for forward signaling and 4 frequencies (6 signals) for backward signaling. Both the forward and backward signals can assume a number of meanings depending on the signaling state. Transition from one set of meanings (called a 'group') to another is controlled by transmission of specific signals. ITU recommendations define 2 groups for forward signals (groups I and II) and 2 for backward signals (groups A and B). Some countries chose to define 3 groups in each direction (I, II and III for forward signals and A, B and C for backward signals). The concept of 'groups' allows more information to be conveyed (2 groups containing up to 15 signals results in 30 signals in each direction) without having to increase the number of signal generators and detectors, which are expensive resources.

The forward channel initiates inter-register signaling with the transmission of the first DNIS digit. Subsequent forward transmission is controlled by the last backward channel signal response.

1.DNIS transmission processing

2.ANI transmission processing

3.Called line condition processing

The backward channel controls inter-register signaling in the sense that after the first DNIS digit transmission, each subsequent forward channel signal is a response to the last backward channel signal.

Following the first DNIS digit, the backward channel directs the collection of the address information according to the inbound application parameters associated with the call. The backward protocol is abstracted into four processing states that correspond to the four blocks of information that are sent by the forward side:

1.DNIS number collection

2.DNIS category

3.ANI number collection

4.ANI category

November 2009 340