NMS CAS for the ADI Service Developer's Reference Manual (6527-22): NEC signaling

NMS CAS for the ADI Service Developer's Reference Manual (6527-22): NEC signaling: "Show Navigation Component Next Topic
NEC signaling

The NEC PBX protocol implements the specifications of the 30 DLI (digital line interface) using PA-30DTS package, as specified in Annex 303-15-B 2/2 from NEC, NEC Australia PTY, LTD.

The NEC PBX protocol is generally a single B bit signaling protocol. The exception to this is the blocking signal, which uses both the A and B bits. The protocol is asymmetric between the TE side (user or application side) and the NT side (network or PBX side). The signaling channels supporting the line signaling of these protocols are referred to as Af and Bf in the forward direction, and Ab and Bb in the backward direction. The forward channel indicates the condition of the outbound switch equipment and reflects the condition of the calling party's line. The backward channel indicates the condition of the called party's line (the inbound equipment). The C and D bits are never used. Their value is fixed at 0 and 1 respectively.

This topic describes NEC line signaling in the following cases:

*

Calls originating from the PBX
*

Calls placed to the PBX

Calls originating from the PBX

The following table illustrates the signaling states of a typical inbound call originating from the PBX:

State


Outbound PBX AfBf


Direction


Inbound terminal
AbBb

Idle




00








00



Ring on




01







00



Ring off




00







00



An incoming call is presented to the application. The application can answer or reject it. If the application answers the call, the line code changes to the conversation state line code after the outbound side re-asserts ring on B signaling bit.



Ring on




01







00



Answer - conversation state




01








01



If the application rejects the call, the protocol does not respond to the ring signal. The calling party eventually abandons the call with the signaling bits for the outbound side remaining in the idle state.

The application disconnects the call, as shown:



Clear back




01








00



Idle




00







00



Calls placed to the PBX

The following table illustrates the signaling states of a typical outbound call placed to the connecting PBX:

State


Outbound terminal
AfBf


Direction


Inbound PBX
AbBb

Idle




00








00



Seizure




01







00



Seizure acknowledge




01





Dial tone




00



Dialing




01




DTMF digits dialed




00



The remote switch either answers or rejects the call. If the call is answered, the answer signal, AB = 01 is asserted. The switch can provide ring tone before answering the call. The outbound TCP performs call progress detection at this phase.



Answer - conversation state




01








01



The application disconnects the call, as shown:



Clear forward




00







01



Idle




00








00"