Signaling Blog

Address Complete (ACM)
Sent in the backward direction indicating all address signals have been received and that the call set-up is progressing

Code: 0 0 0 0 0 1 1 0

Answer (ANM)
Sent in the backward direction to indicate that the called party has answered the call. May be used to trigger billing and measurements of call duration

Code: 0 0 0 0 1 0 0 1

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

Code: 0 0 0 1 0 0 1 1

Blocking Ack (BLA)
Sent as a response to a block message indicating that the identified circuit has been blocked to outgoing traffic

Code: 0 0 0 1 0 1 0 1

Call Progress (CPG)
Sent in either direction indicating that an event has occurred in the progress of a call

Code: 0 0 1 0 1 1 0 0

Circuit Group Blocking (CGB)
Sent for maintenance purposes to the exchange at the far end of a group of circuits to cause the engaged condition of those circuits

Code: 0 0 0 1 1 0 0 0

Circuit Group Blocking Ack. (CGBA)
Sent in response to a CGB indicating the identified group of circuits have been blocked to outgoing traffic

Code: 0 0 0 1 1 0 1 0

Circuit Group Query (CGQ) (N) (I) (Q)
[Circuit Query Message (ANSI)]
Sent on a routine or demand basis to request the exchange at the other end of a group of circuits five the state of the circuits within the specified range

Code: 0 0 1 0 1 0 1 0

Circuit Group Query Response (CQR)
[Circuit Query Response Message (ANSI)]
Sent in response to a CGQ indicating the state of the previously identified group of circuits

Code: 0 0 1 0 1 0 1 1

Exit Message (EXM) (A)
Sent in the backward direction from an outgoing gateway exchange to indicate that the call has successfully progressed to the adjacent network Intra-network use only

Code: 1 1 1 0 1 1 0 1

Facility (FAC)
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 previously requested action

Code: 0 0 1 1 0 0 1 1

Facility Accepted (FAA) (I) (Q)
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 previously requested action

Code: 0 0 1 1 0 0 1 1

Facility Reject (FAJ) (I) (Q)
Sent from one exchange to another to request activation of a facility

Code: 0 0 1 0 0 0 0 1

Facility Request (FAR) (I) (Q)
Sent from one exchange to another to request activation of a facility

Code: 0 0 1 0 0 0 0 1

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

Code: 0 0 0 1 1 1 1 1

Identification Request (IDR) (I)
Sent in either direction to request an action regarding the malicious call identification supplementary service

Code: 0 0 1 1 0 1 1 0

Identification Response (IDS) (I)
Sent in response to the IDR message

Code: 0 0 1 1 0 1 1 1

Information (INF) (N) (Q)
Sent to convey additional call related information which may have been request in the INR message

Code: 0 0 0 0 0 1 0 0

Information Request (INR) (N) (Q)
Sent by an exchange to request additional call related information

Code: 0 0 0 0 0 0 1 1

Loop Back Acknowledgement (LPA) (N)
Sent as a response to a CCR to indicate that the requested loop back has been connected (or transceiver in the case 2 wire connection)

Code: 0 0 1 0 0 1 0 0

Loop Prevention (LOP) (I) (N97)
Sent to convey information required by the ECT supplementary service.

Code: 0 1 0 0 0 0 0 0

Network Resource Management (NRM) (I)
Sent in order to modify network resources associated with a certain call, sent along an established path in any direction in any phase of the call

Code: 0 0 1 1 0 0 1 0

Overload (OLM) (N) (I)
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

Code: 0 0 1 1 0 0 0 0

Pass-Along (PAM) (N) (Q)
Sent in either direction to transfer information between two signalling points along the same signalling path as that used to establish a physical connection

Code: 0 0 1 0 1 0 0 0

Pre-Release Information (PRI) (I) (N99)
Sent containing information which if included in the Release message itself would cause compatibility problems with ISUP 1992 and subsequent versions of the ISUP protocol.

Code: 0 1 0 0 0 0 1 0

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

Code: 0 0 0 0 1 1 0 0

Release Complete (RLC)
Sent in either direction as a response to a REL or RSC message to indicate that the circuit has been brought into the idle state

Code: 0 0 0 1 0 0 0 0

Reset Circuit (RSC)
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

Code: 0 0 0 1 0 0 1 0

Resume (RES)
Sent in the backward direction to indicate re-answer from an inter-working node or that a non ISDN called party has gone off hook within a certain time after going on-hook during the active phase of the call

Code: 0 0 0 0 1 1 1 0

Segmentation (SGM) (I)
Sent in either direction to convey another part of an overlength message.

Code: 0 0 1 1 1 0 0 0

Subsequent address (SAM) (I)
Sent in either direction to convey an additional segment of an over length message

Code: 0 0 0 0 0 0 1 0

Subsequent Directory Number (SDN) (N) (I) (Q) (N99)
Sent in the forward direction following an IAM message. It conveys additional called party number information.

Code: 0 1 0 0 0 0 1 1

Suspend (SUS)
Sent in the backward direction to indicate clear back from an inter-working exchange or a non ISDN called party has gone on hook during the active state of a call

Code: 0 0 0 0 1 1 0 1

Unblocking (UBL)
Sent to cancel the engaged condition of a circuit caused by a previously sent BLO message

Code: 0 0 0 1 0 1 0 0

Unblocking acknowledgement (UBA)
Sent in response to a UBL indicating the identified circuit is now in the idle state (unblocked)

Code: 0 0 0 1 0 1 1 0

Unequipped CIC (UCIC) (N)
Sent from one exchange to another when it receives a message that contains an unequipped circuit identification code

Code: 0 0 1 0 1 1 1 0

User Part Available (UPA) (I)
Sent in either direction as a response to a user part test message, to indicate that the user part is available

Code: 0 0 1 1 0 1 0 1

User Part test (UPT) (I)
Sent in either direction to test the status of a user part marked as independent of call control message

Code: 0 0 1 1 0 1 0 0

User-to-user information (USR) (I) (Q)
Used for transport of user-to-user signalling independent of call control messages

Code: 0 0 1 0 1 1 0 1

Key:
(A) MESSAGES SUPPORTED IN ANSI ONLY
(I) MESSAGES SUPPORTED IN ITU ONLY
(N) ITU - NATIONAL USE
(NS67) MESSAGES NOT SUPPORTED IN ITU INTERNATIONAL ISUP Q.767
(NI99) NEW IN ITU ISUP 99
(NI97) NEW IN ITU ISUP 97