You are here: CSP Developer’s Guide: Common Channel Signaling > A Appendix > ISUP Signaling Messages
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 |
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 |
|
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 |
1 Messages supported in ANSI only
2 Messages supported in ITU only
3 ITU - National use