Message Code

ID

Description

Purpose

ACM

0x06

Address Complete Message

Sent in the backward direction indicating that all required data has been received and the call set-up is progressing

ANM

0x09

Answer Message

Sent in the backward direction to indicate that the called party has answered the call, may be used to trigger billing and call

BLA

0x15

Blocking Acknowledgment

Sent as a response to a BLO message indicating the identified circuit has

BLO 1

0x13

Blocking

Sent for maintenance purposes to the exchange at the other end of the circuit to cause an engaged condition of that circuit (receive only)

CCL

Calling Party Clear

CCR

0x11

Continuity Check Request

Sent to request a non-call-related continuity check on the identified circuit

CFN

0x2F

Confusion

Sent in response to any message (other than a confusion message) to indicate that all or part of a received message was unrecognized

CGB

0x18

Circuit Group Blocking

Sent for maintenance purposes to the exchange at the far end of a group of circuits to cause the engaged condition of those circuits

CGBA

0x1A

Circuit Group Blocking Acknowledgment

Sent as a response to a CGB indicating that the identified group of circuits has been blocked to outgoing traffic

CGU

0x19

Circuit Group Unblocking

Sent to cancel the engaged condition of a group of circuits caused by a previously sent CGB message.

CGUA

0x1B

Circuit Group Unblocking Acknowledgment

Sent in response to a CGU indicating the identified group of circuits are now in the idle state

CMC 3

0x1D

Call Modification Complete

Message sent in either direction to indicate that the call modification request has been accepted

CMR3

0x1C

Call Modification Request

Message sent in either direction to request a change in the call characteristics

CMRJ 3

0x1E

Call Modification Reject

Message sent in either direction to indicate that the call modification request has been rejected

CON 2

0x0F

Connect

Sent in the backward direction indicating that all the address signals required for routing the call to the called party have been received and that the call has been answered

COT

0x05

Continuity

Sent in the forward direction to indicate the result of the completed continuity test

CPG

0x2C

Call Progress

Sent in either direction indicating that an event of significance to the originating or terminating access has occurred

CQM 3

0x2A

Circuit Query Message

Sent on a routine or demand basis to request the exchange at the other end of a group of circuits give the state of the circuits within the specified range

CQR 3

0x2B

Circuit Query Response

Sent in response to a CQM indicating the state of the previously identified group of circuits.

CRA 1

0xE9

Circuit Reservation Acknowledgment

Sent in the backward direction in response to a CRM indicating that the circuit has been reserved for an incoming call

CRG 2

0x31

Charge Information

Information sent in either direction for accounting and/or call charging purposes. national use only

CRM 1

0xEA

Circuit Reservation Message

Sent in the forward direction only when interworking with exchange access MF signaling to reserve a circuit and initiate any required continuity check

CVR 1

0xEB

Circuit Validation Response

Sent in response to a CVT to convey translation information for the indicated circuit

CVT 1

0xEC

Circuit Validation Test

Sent on a routine or demand basis to request translation information for the identified circuit

DRS 2/3

0x27

Delayed Release

Sent in either direction to indicate that the called or calling party has disconnected while the network is still holding the connection

En-block calls

Address digits are transmitted in one or more blocks.

In this form of signaling, address digits are transmitted in one or more blocks, and each block contains enough address information to enable the CSP to carry out forward routing.

EXM 1

0xED

Exit Message

Sent in the backward direction from an outgoing gateway exchange to indicate that the call has successfully progressed to the adjacent network

FAA 2

0x20

Facility Accept

Sent in response to a facility request message indicating that the requested facility has been invoked

FAC 3

0x33

Facility Message

Sent in either direction at any phase of a call to request an action at another exchange. Also used to carry the results, error or rejection of a previously requested action

FAR 2

0x1F

Facility Request

Sent from one exchange to another to request activation of a facility

FOT

0x08

Forward Transfer

Sent in the forward direction on semi-automatic calls when the operator wants the help of an operator at a distant exchange

FRJ 2

0x21

Facility Reject

Sent in response to a facility request message indicating that the facility request has been rejected

GRA

0x29

Circuit Group Reset Acknowledgment

Sent in response to a GRS message to indicate the group of circuits have been realigned

GRS

0x17

Circuit Group Reset

Sent to align the state of a group of circuits, release any calls in progress remove any remotely blocked state.

IAM

0x01

Initial Address Message

Sent in the forward direction to initiate seizure of an outgoing circuit.

May also request continuity test on identified circuit

IDR 2

0x36

Identification Request

Sent in either direction to request an action regarding the malicious call identification supplementary service

IDS 2

0x37

Identification Response

Sent in response to the identification request message

INF 3

0x04

Information

Sent to convey additional call-related information which may have been requested in the inr message

INR 3

0x03

Information Request

Sent by an exchange to request additional call related information

IRS

Identification

LPA 3

Loopback Acknowledge

MCP

Message Compatibility Procedure

MPM

Meter Pulse Message

NRM 2

Network Resource Management

Sent in order to modify network resources associated with a certain call, sent along an established path in any direction in any phase of a call

OLM 2/3

Overload Message

Sent in the backward direction, on non-priority calls in response to an iam, to invoke temporary trunk blocking of the circuit concerned when the exchange generating the message is subject to load control

OPR

Operator

PAM 3

0x28

Pass Along Message

Sent in either direction to transfer information between two signaling points along the same signaling path as that used to establish a physical connection.

PCP

Parameter Compatibility procedure

PDC

Propagation Delay Counter

REL

0x0C

Release

Sent in either direction indicating that the circuit identified in the message is being released and the cause for the release

RES

0x0E

Resume

Sent in the backward direction to indicate re-answer from an interworking node or that a non-ISDN called party has gone off hook

RLC

0x10

Release Complete

Sent in either direction as a response to a release message or a reset circuit message to indicate that the circuit has been brought into the idle state

RSC

0x12

Reset Circuit

Sent when an exchange does not know the state of a particular circuit and wants to release any call in progress, remove any remotely blocked state and align states

SAM 2

0x02

Subsequent Address Message

Sent in the forward direction to convey an additional segment of an overlength message after the IAM and before the ACM.

SGM 2

0x38

Segmentation Message

Sent in either direction to convey an additional segment of an overlength message

SUS

0x0D

Suspend

Sent in the backward direction to indicate clear back from an interworking exchange or a non-ISDN called party has gone on hook

TTB

Temporary Trunk Blocking

UBA

0x16

Unblocking Acknowledgment

Sent in response to a UBL indicating the identified circuit is now in the idle state

UBL

0x14

Unblocking

Sent to cancel the engaged condition of a circuit caused by a previously sent BLO message

UCIC 3

0x2E

Unequipped CIC

Sent from one exchange to another when it receives a message that contains an unequipped circuit identification code

UPA 2

0x35

User Part Available

Sent in either direction as a response to a user part test message, to indicate that the user part is available

UPT 2

0x34

User Part Test

Sent in either direction to test the status of a user part marked as independent of call control messages

USR 2

0x2D

User-Defined

Used for transport of user-to-user signaling independent of call control messages