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Recommendation Q.762

GENERAL FUNCTION OF MESSAGES AND SIGNALS

    This Recommendation describes the elements of signalling informa-
tion used by the ISDN User Part protocol and their function. The
encoding of these elements, the format of the messages in which they
are conveyed and their application in the ISDN User Part signalling
procedures are described in Recommendations Q.763 and Q.764.
Table1/Q.762 gives the mandatory or optional parameters in the
ISDN user part messages and Table 2/Q.762 the list of abbreviations
of these messages.

1        Signalling messages

1.1    Address complete message (ACM)

    A message sent in the backward direction indicating that all the
address signals required for routing the call to the called party have been
received.

1.2    Answer message (ANM)

    A message sent in the backward direction indicating that the call has
been answered. In semiùautomatic working this message has a supervisory
function. In automatic working this message is used in conjunction with
charging information in order to:

ù    start metering the charge to the calling subscriber (see Recommen-
dation Q.28), and

ù    start measurement of call duration for international accounting pur-
poses (Recommendation E.260).

1.3    Blocking message (BLO)

    A message sent only for maintenance purposes to the exchange at the
other end of a circuit, to cause an engaged condition of that circuit for sub-
sequent calls outgoing from that exchange. When a circuit is used in the
bothway mode of operation an exchange receiving the blocking message
must be capable of accepting incoming calls on the concerned circuit unless
it has also sent a blocking message. Under certain conditions, a blocking
message is also a proper response to a reset circuit message.

1.4    Blocking acknowledgement message (BLA)

    A message sent in response to a blocking message indicating that the
circuit has been blocked.

1.5    Call modification completed message (CMC)

    A message sent in response to a call modification request message
indicating that the requested call modification (e.g. from voice to data) has
been completed.

1.6    Call modification reject message (CMRJ)

    A message sent in response to a call modification request message
indicating that the request has been rejected.

1.7    Call modification request message (CMR)

    A message sent in either direction indicating a calling or called party
request to modify the characteristics of an established call (e.g. from data to
voice).

1.8    Call progress message (CPG)

    A message sent in the backward direction indicating that an event has
occurred during call setùup which should be relayed to the calling party.

1.9    Charge information message (CRG) (national use)

    Information sent in either direction for accounting and/or call charg-
ing purposes.

1.10    Circuit group blocking message (CGB)

    A message sent to the exchange at the other end of an identified group
of circuits to cause an engaged condition of this group of circuits for subse-
quent calls outgoing from that exchange. An exchange receiving a circuit
group blocking message must be able to accept incoming calls on the group
of blocked circuits unless it has also sent a blocking message. Under certain
conditions, a circuit group blocking message is also a proper response to a
reset circuit message.

1.11    Circuit group blocking acknowledgement message (CGBA)

    A message sent in response to a circuit group blocking message to
indicate that the requested group of circuits has been blocked.

1.12    Circuit group reset message (GRS)

    A message sent to release an identified group of circuits when, due to
memory mutilation or other causes, it is unknown whether for example, a
release or release complete message is appropriate for each of the circuits in
the group. If at the receiving end a circuit is remotely blocked, reception of
this message should cause that condition to be removed.

1.13    Circuit group reset acknowledgement message (GRA)

    A message sent in response to a circuit group reset message and indi-
cating that the requested group of circuits has been reset. The message also
indicates the maintenance blocking state of each circuit.

1.14    Circuit group unblocking message (CGU)

    A message sent to the exchange at the other end of an identified group
of circuits to cause cancellation in that group of circuits of an engaged con-
dition invoked earlier by a blocking or circuit group blocking message.

1.15    Circuit group unblocking acknowledgement message (CGUA)

    A message sent in response to a circuit group unblocking message to
indicate that the requested group of circuits has been unblocked.

1.16    Circuit group query message (CQM)

    A message sent on a routine or demand basis to request the farùend
exchange to give the state of all circuits in a particular range.

1.17    Circuit group query response message (CQR)

    A message sent in response to a circuit group query message to indi-
cate the state of all circuits in a particular range.

1.18    Confusion message (CFN)

    A message sent in response to any message (other than a confusion
message) if the exchange does not recognize the message or detects a part of
the message as being unrecognized.

1.19    Connect message (CON)

    A message 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.

1.20    Continuity message (COT)

    A message sent in the forward direction indicating whether or not
there is continuity on the preceding circuit(s) as well as of the selected cir-
cuit to the following exchange, including verification of the communication
path across the exchange with the specified degree of reliability.

1.21    Continuity check request message (CCR)

    A message sent by an exchange for a circuit on which a continuity
check is to be performed, to the exchange at the other end of the circuit,
requesting continuity checking equipment to be attached.

1.22    Delayed release message (DRS) (national use)

    A message sent in either direction indicating that the called or calling
party has disconnected but that the network is holding the connection.

1.23    Facility accepted message (FAA)

    A message sent in response to a facility request message indicating
that the requested facility has been invoked.

1.24    Facility reject message (FRJ)

    A message sent in response to a facility request message to indicate
that the facility request has been rejected.

1.25    Facility request message (FAR)

    A message sent from an exchange to another exchange to request acti-
vation of a facility.

1.26    Forward transfer message (FOT)

    A message sent in the forward direction on semiùautomatic calls
when the outgoing international exchange operator wants the help of an
operator at the incoming international exchange. The message will normally
serve to bring an assistance operator (see Recommendation Q.101) into the
circuit if the call is automatically set up at the exchange. When the call is
completed via an operator (incoming or delay operator) at the incoming
international exchange, the message should preferably cause this operator to
be recalled.

1.27    Information message (INF)

    A message sent to convey information in association with a call,
which may have been requested in an information request message.

1.28    Information request message (INR)

    A message sent by an exchange to request information in association
with a call.

1.29    Initial address message (IAM)

    A message sent in the forward direction to initiate seizure of an out-
going circuit and to transmit number and other information relating to the
routing and handling of a call.

1.30    Loop back acknowledgement message (LPA) (national use)

    A message sent in the backward direction in response to a continuity
check request message indicating that a loop (or transceiver in the case of a
2ùwire circuit) has been connected.

1.31    Overload message (OLM) (national use)

    A message sent in the backward direction, on nonùpriority calls in
response to an IAM, to invoke temporary trunk blocking of the circuit con-
cerned when the exchange generating the message is subject to load control.

1.32    Passùalong message (PAM)

    A message that may be sent in either direction to transfer information
between two signalling points along the same signalling path as that used to
establish a physical connection between those two points.

1.33    Release message (REL)

    A message sent in either direction to indicate that the circuit is being
released due to the reason (cause) supplied and is ready to be put into the
idle state on receipt of the release complete message. In case the call was
forwarded or is to be rerouted, the appropriate indicator is carried in the
message together with the redirection address and the redirecting address.

1.34    Release complete message (RLC)

    A message sent in either direction in response to the receipt of a
released message, or if appropriate to a reset circuit message, when the cir-
cuit concerned has been brought into the idle condition.

1.35    Reset circuit message (RSC)

    A message sent to release a circuit when, due to memory mutilation or
other causes, it is unknown whether for example, a release or a release com-
plete message is appropriate. If, at the receiving end, the circuit is remotely
blocked, reception of this message should cause that condition to be
removed.

1.36    Resume message (RES)

    A message sent in either direction indicating that the calling or called
party, after having been suspended, is reconnected.

1.37    Subsequent address message (SAM)

    A message that may be sent in the forward direction following an ini-
tial address message, to convey additional called party number information.

1.38    Suspend message (SUS)

    A message sent in either direction indicating that the calling or called
party has been temporarily disconnected.

1.39    Unblocking message (UBL)

    A message sent to the exchange at the other end of a circuit to cancel,
in that exchange, the engaged condition of the circuit caused by a previously
sent blocking or circuit group blocking message.

1.40    Unblocking acknowledgement message (UBA)

    A message sent in response to an unblocking message indicating that
the circuit has been unblocked.

1.41    Unequipped circuit identification code message (UCIC) (national use)

    A message sent from one exchange to another when it receives an
unequipped circuit identification code.

1.42    Userùtoùuser information message (USR)

    A message to be used for the transport of userùtoùuser signalling
independent of call control messages.

2    Signalling information

2.1    Access transport

    Information generated on the access side of a call and transferred
transparently in either direction between originating and teminating local
exchanges. The information is significant to both users and local exchanges.

2.2    Address presentation restricted indicator

    Information sent in either direction to indicate that the address infor-
mation is not to be presented to a public network user, but can be passed to
another public network. It may also be used to indicate that the address can-
not be ascertained.

2.3    Address signal

    An element of information in a network number. The address signal
may indicate digit values 0 to 9, code 11 or code 12. One address signal
value (ST) is reserved to indicate the end of the called party number.

2.4    Automatic congestion level

    Information sent to the exchange at the other end of a circuit to indi-
cate that a particular level of congestion exists at the sending exchange.

2.5    Call forwarding may occur indicator

    Information sent in the backward direction indicating that call for-
warding may occur, depending on the response received (or lack thereof)
from the called party.

2.6    Call identity

    Information sent in the call reference parameter indicating the identity
of a call in a signalling point.

2.7    Call reference

    Circuit independent information identifying a particular call.

2.8    Called party number

    Information to identify the called party.

2.9    Called party's category indicator

    Information sent in the backward direction indicating the category of
the called party, e.g. ordinary subscriber or payphone.

2.10    Called party's status indicator

    Information sent in the backward direction indicating the status of the
called party, e.g. subscriber free.

2.11    Calling party number

    Information sent in the forward direction to identify the calling party.

2.12    Calling party address request indicator

    Information sent in the backward direction indicating a request for the
calling party address to be returned.

2.13    Calling party address response indicator

    Information sent in response to a request for the calling party address,
indicating whether the requested address is included, not included, not
available or incomplete.

2.14    Calling party number incomplete indicator

    Information sent in the forward direction indicating that the complete
calling party number is not included.

2.15    Calling party's category

    Information sent in the forward direction indicating the category of
the calling party and, in case of semiùautomatic calls, the service language
to be spoken by the incoming, delay and assistance operators.

2.16    Calling party's category request indicator

    Information sent in the backward direction indicating a request for the
calling party's category to be returned.

2.17    Calling party's category response indicator

    Information sent in response to a request for the calling party's cate-
gory, indicating whether or not the requested information is included in the
response.

2.18    Cause value

    Information sent in either direction indicating the reason for sending
the message (e.g. release message). Definitions for each cause value are
listed below.

a)    Normal class

Cause 1 ù Unallocated (unassigned) number

    This cause indicates that the called party cannot be reached because,
although the called party number is in a valid format, it is not cur-
rently allocated (assigned).

Cause 2 ù No route to specified transit network

    This cause indicates that the equipment sending this cause has
received a request to route the call through a particular transit net-
work which it does not recognize. The equipment sending this
cause does not recognize the transit network either because the
transit network does not exist or because that particular transit net-
work, while it does exist, does not serve the equipment which is
sending this cause. This cause is supported on a networkùdepen-
dent basis.

Cause 3 ù No route to destination

    This cause indicates that the called party cannot be reached because
the network through which the call has been routed does not serve
the destination desired. This cause is supported on a networkù
dependent basis.

Cause 4 ù Send special information tone

    This cause indicates that the called party cannot be reached for rea-
sons that are of longùterm nature and that the special information
tone should be returned to the calling party.

Cause 5 ù Misdialled trunk prefix

    This cause indicates the erroneous inclusion of a trunk prefix in the
called party number (for national use only).

Cause 16 ù Normal call clearing

    This cause indicates that the call is being cleared because one of the
users involved in the call has requested that the call be cleared.
Under normal situation, the source of this cause is not the network.

Cause 17 ù User busy

    This cause is used when the called party has indicated the inability to
accept another call. It is noted that the user equipment is compati-
ble with the call.

Cause 18 ù No user responding

        This cause is used when a called party does not respond to a call
establishment message with either an alerting or conect indication
within the prescribed period of time.

Cause 19 ù No answer from user (user alerted)

    This cause is used when the called party has been alerted but does not
respond with a connect indication within the prescribed period of
time.

Cause 21 ù Call rejected

    This cause indicates that the equipment sending this cause does not
wish to accept this call, although it could have accepted the call
because the equipment sending this cause is neither busy or incom-
patible.

Cause 22 ù Number changed

    This cause is returned to a calling party when the called number indi-
cated by the calling party is no longer assigned. The new called
number may optionally be included in the diagnostic field. If a net-
work does not support this capability, cause number 1 shall be
used.

Cause 27 ù Destination out of order

    This cause indicates that the destination requested by the user cannot
be reached because the interface to the destination is not function-
ing correctly. The term ônot functioning correctlyö indicates that a
signalling message was unable to be delivered to the remote party;
e.g. a physical layer or data link layer failure at the remote party,
user equipment offùline, etc.

Cause 28 ù Address incomplete

    This cause indicates that the called party cannot be reached because
the called party number is not in a valid format or is not complete.
This condition may be determined in the incoming international
exchange (or in the national destination network):

ù    immediately after reception of an ST signal, or

ù    on timeùout after the last received digit.

Cause 29 ù Facility rejected

    This cause is returned when a supplementary service requested by the
user cannot be provided by the network.

Cause 31 ù Normal, unspecified

    This cause is used to report a normal event only when no other cause
in the normal class applies.

b)    Resource Unavailable class

Cause 34 ù No circuit available

    This cause indicates that there is no appropriate circuit presently
available to handle the call.

Cause 38 ù Network out of order

    This cause indicates that the network is not functioning correctly and
that the condition is likely to last a relatively long period of time,
e.g. immediately reùattempting the call is not likely to be success-
ful.

Cause 41 ù Temporary failure

    This cause indicates that the network is not functioning correctly and
that the condition is not likely to last a long period of time, e.g. the
use may wish to try another call attempt almost immediately.

Cause 42 ù Switching equipment congestion

    This cause indicates that the switching equipment generating this
cause is experiencing a period of high traffic.

Cause 47 ù Resource unavailable, unspecified

    This cause is used to report a resource unavailable event only when
no other cause in the resource unavailable class applies.

c)    Service or Option Not Available class

Cause 50 ù Requested facility not subscribed

    This cause indicates that the user has requested a supplementary ser-
vice which is implemented by the equipment which generated this
cause, but the user is not authorized to use.

Cause 55 ù Incoming calls barred within CUG

    This cause indicates that although the called party is a member of the
CUG for the incoming CUG call, incoming calls are not allowed
within this CUG.

Cause 57 ù Bearer capability not authorized

    This cause indicates that the user has requested a bearer capability
which is implemented by the equipment which generated this
cause but the user is not authorized to use.

Cause 58 ù Bearer capability not presently available

    This cause indicates that the user has requested a bearer capability
which is implemented by the equipment which generated this
cause but which is not available at this time.

Cause 63 ù Service or option not available, unspecified

    This cause is used to report a service or option not available event
only when no other cause in the service or option not available
class applies.

d)    Service or Option Not Implemented class

Cause 65 ù Bearer capability not implemented

    This cause indicates that the equipment sending this cause does not
support the bearer capability requested.

Cause 69 ù Requested facility not implemented

    This cause indicates that the equipment sending this cause does not
support the requested supplementary service.

Cause 70 ù Only restricted digital information bearer capability is
available

    This cause indicates that the calling party has requested an unre-
stricted bearer service but that the equipment sending this cause
only supports the restricted version of the requested bearer capabil-
ity.

Cause 79 ù Service or option not implemented, unspecified

    This cause is used to report a service or option not implemented event
only when no other cause in the service or option not implemented
class applies.

e)    Invalid Message (e.g. Parameter out of Range) class

Cause 87 ù Called user not member of CUG

    This cause indicates that the called user for the incoming CUG call is
not a member of the specified CUG.

Cause 88 ù Incompatible destination

    This cause indicates that the equipment sending this cause has
received a request to establish a call which has low layer compati-
bility or high layer compatibility or other compatibility attributes
(e.g. data rate) which cannot be accommodated.

Cause 91 ù Invalid transit network selection

    This cause indicates that a transit network identification was received
which is of an incorrect format as defined in Annex C of Recom-
mendation Q.931.

Cause 95 ù Invalid message, unspecified

    This cause is used to report an invalid message event only when no
other cause in the invalid message class applies.

f)    Protocol error (e.g. Unknown Message) class

Cause 97 ù Message type nonùexistent or not implemented

    This cause indicates that the equipment sending this cause has
received a message which it does not recognize either because this
is a message type not defined or defined but not implemented by
the equipment sending this cause.

Cause 99 ù Parameter nonùexistent or not implemented ù dis-
carded

    This cause indicates that the equipment sending this cause has
received a message which includes parameters not recognized
because the parameters are not defined or are defined but not
implemented by the equipment sending the cause. The cause indi-
cates that the parameter(s) were discarded.

Cause 103 ù Parameter nonùexistent or not implemented ù
passed on

    This cause indicates that the equipment sending this cause has
received a message which includes parameters not recognized
because the parameters are not defined or are defined but not
implemented by the equipment sending the cause. The cause indi-
cates that the parameter(s) were ignored. In addition, if the equip-
ment sending this cause is an intermediate point, then this cause
indicates that the parameter(s) were passed on unchanged.

Cause 111 ù Protocol error, unspecified

    This cause is used to report a protocol error event only when no other
cause in the protocol error class applies.

g)    Interworking class

Cause 127 ù Interworking, unspecified

    This cause indicates that there has been interworking with a network
which does not provide causes for actions it takes; thus, the precise
cause for a message which is being sent cannot be ascertained.

2.19    Charge indicator

    Information sent in the backward direction indicating whether or not
the call is chargeable.

2.20    Charge information request indicator (national use)

    Information sent in either direction requesting charge information to
be returned.

2.21    Charge information response indicator (national use)

    Information sent in response to a request for charge information indi-
cating whether or not the requested information is included.

2.22    Circuit group supervision message type indicator

    Information sent in a circuit group blocking or unblocking message,
indicating whether blocking (unblocking) is maintenance oriented or hard-
ware oriented.

2.23    Circuit identification code

    Information identifying the physical path between a pair of
exchanges.

2.24    Circuit state indicator

    Information indicating the state of a circuit according to the sending
exchange.

2.25    Closed user group call indicator

    Information indicating whether or not the concerned call can be set up
as a closed user group call and, if a closed user group call, whether or not
outgoing access is allowed.

2.26    Closed user group interlock code

    Information uniquely identifying a closed user group within a net-
work.

2.27    Coding standard

    Information sent in association with a parameter (e.g. cause indica-
tors) identifying the standard in which the parameter format is described.

2.28    Connected number

    Information sent in the backward direction to identify the connected
party.

2.29    Connection request

    Information sent in the forward direction on behalf of the signalling
connection control part requesting the establishment of an endùtoùend
connection.

2.30    Continuity check indicator

    Information sent in the forward direction indicating whether or not a
continuity check will be performed on the circuit(s) concerned or is being
(has been) performed on a previous circuit in the connection.

2.31    Continuity indicator

    Information sent in the forward direction indicating whether or not the
continuity check on the outgoing circuit was successful. A continuity check
successful indication also implies continuity of the preceding circuits and
successful verification of the path across the exchange with the specified
degree of reliability.

2.32    Credit

    Information sent in a connection request, indicating the window size
requested by the signalling connection control part for an endùtoùend
connection.

3.33    Diagnostic

    Information sent in association which a cause value and which pro-
vides supplementary information about the reason for sending the message.

2.34    Echo control device indicator

    Information indicating whether or not a half echo control device is
included in the connection.

2.35    Endùtoùend information indicator

    Information sent in either direction indicating whether or not the
sending exchange has further call information available for endùtoùend
transmission. In the forward direction, an indication that endùtoùend
information is available will imply that the destination exchange may obtain
the information before alerting the called party.

2.36    Endùtoùend method indicator

    Information sent in either direction indicating the available methods,
if any, for endùtoùend transfer of information.

2.37    Event indicator

    Information sent in the backward direction indicating the type of
event which caused a call progress message to be sent to the originating
local exchange.

2.38    Event presentation restricted indicator

    Information sent in the backward direction indicating that the event
should not be presented to the calling party.

2.39    Extension indicator

    Information indicating whether or not the associated octet has been
extended.

2.40    Facility indicator

    Information sent in facility related messages identifying the facility or
facilities with which the message is concerned.

2.41    Holding indicator (national use)

    Information sent in either direction indicating that holding of the con-
nection is requested.

2.42    Hold provided indicator (national use)

    Information sent in either direction indicating that the connection will
be held after the calling or called party has attempted to release.

2.43    Inùband information indicator

    Information sent in the backward direction indicating that inùband
information or an appropriate pattern is now available.

2.44    Internal network number indicator

    Information sent to the destination exchange indicating whether or not
the call is allowed should the called party number prove to be an internal
network number (e.g. mobile access point).

2.45    Interworking indicator

    Information sent in either direction indicating whether or not Signal-
ling System No. 7 is used in all parts of the network connection.

2.46    ISDN access indicator

    Information sent in either direction indicating whether or not the
access signalling protocol is ISDN.

2.47    ISDN user part indicator

    Information sent in either direction to indicate that the ISDN user part
is used in all preceding parts of the network connection. When sent in the
backward direction, the preceding parts are those towards the called party.

2.48    ISDN user preference indicator

    Information sent in the forward direction indicating whether or not the
ISDN user part is required or preferred in all parts of the network connec-
tion.

2.49    Local reference

    Information sent in the connection request, indicating the local refer-
ence allocated by the signalling connection control part to an endùtoùend
connection.

2.50    Location

    Information sent in either direction indicating where an event (e.g.
release) was generated.

2.51    Malicious call identification request indicator (national use)

    Information sent in the backward direction to request the identity of
the calling party for the purpose of malicious call idenification.

2.52    Modification indicator

    Information sent in the call modification indicators parameter indicat-
ing whether the call modification is to service 1 or service 2.

2.53    National/international call indicator

    Information sent in the forward direction indicating in the destination
national network whether the call has to be treated as an international call or
as a national call.

2.54    Nature of address indicator

    Information sent in association with an address indicating the nature
of that address, e.g. ISDN international number, ISDN national significant
number, or ISDN subscriber number.

2.55    Numbering plan indicator

    Information sent in association with a number indicating the number-
ing plan used for that number (e.g. ISDN number, Telex number).

2.56    Odd/even indicator

    Information sent in association with an address, indicating whether
the number of address signals contained in the address is even or odd.

2.57    Original called number

    Information sent in the forward direction when a call is redirected and
identifies the original called party.

2.58    Original redirection reason

    Information sent in either direction indicating the reason why the call
was originally redirected.

2.59    Point code

    Information sent in the call reference parameter indicating the code of
the signalling point in which the call identity allocated to the call reference
is relevant.

2.60    Protocol class

    Information sent in the connection request parameter indicating the
protocol class requested by the signalling connection control part for the
endùtoùend connection.

2.61    Protocol control indicator

    Information consisting of the endùtoùend method indicator, the
interworking indicator, the endùtoùend information indicator, the SCCP
method indicator and the ISDN user part indicator. The protocol control
indicator is contained in both the forward and backward call indicators
parameter field and describes the signalling capabilities within the network
connection.

2.62    Range

    Information sent in a circuit group supervision message (e.g. circuit
group blocking) to indicate the range of circuits affected by the action in the
message.

2.63    Recommendation indicator

    Information sent in association with a cause value identifying the
Recommendation to which the cause value applies.

2.64    Redirecting indicator

    Information sent in either direction indicating whether the call has
been forwarded or rerouted and whether or not presentation of redirection
information to the calling party is restricted.

2.65    Redirecting number

    Information sent in the forward direction when a call is redirected
more than once, indicating the number from which the call was last redi-
rected.

2.66    Redirecting reason

    Information sent in either direction indicating, in the case of calls
undergoing multiple redirections, the reason why the call has been redi-
rected.

2.67    Redirection counter

    Information sent in either direction indicating the number of redirec-
tions which have occurred on a call.

2.68    Redirection number

    Information sent in the backward direction indicating the number
towards which the call must be rerouted or has been forwarded.

2.69    Routing label

    Information provided to the message transfer part for the purpose of
message routing (see RecommendationQ.704, º 2.2).

2.70    Satellite indicator

    Information sent in the forward direction indicating the number of sat-
ellite circuits in the connection.

2.71    SCCP method indicator

    Information sent in either direction indicating the available SCCP
methods, if any, for endùtoùend transfer of information.

2.72    Screening indicator

    Information sent in either direction to indicate whether the address
was provided by the user or network.

2.73    Signalling point code (national use)

    Information sent in a release message to identify the signalling point
in which the call failed.

2.74    Solicited information indicator

    Information sent in an information message to indicate whether or not
the message is a response to an information request message.

2.75    Status

    Information sent in a circuit group supervision message (e.g. circuit
group blocking) to indicate the specific circuits, within the range of circuits
stated in the message, that are affected by the action specified in the mes-
sage.

2.76    Suspend/Resume indicator

    Information sent in the suspend and resume messages to indicate
whether suspend/resume was initiated by an ISDN subscriber or by the net-
work.

2.77    Temporary trunk blocking after release (national use)

    Information sent to the exchange at the other end of a circuit (trunk)
to indicate low level of congestion at the sending exchange and that the cir-
cuit (trunk) should not be reùoccupied by the receiving exchange for a
short period of time after release.

2.78    Transit network selection (national use)

    Information sent in the initial address message indicating the transit
network(s) requested to be used in the call.

2.79    Transmission medium requirement

    Information sent in the forward direction indicating the type of trans-
mission medium required for the connection (e.g. 64 kbit/s unrestricted,
speech).

2.80    User service information

    Information sent in the forward direction indicating the bearer capa-
bility requested by the calling party.

2.81    Userùtoùuser indicators

    Information sent in association with a request (or response to a
request) for userùtoùuser signalling supplementary service(s).

2.82    Userùtoùuser information

    Information generated by a user and transferred transparently through
the interexchange network between the originating and terminating local
exchanges.

TABLE 1/Q.762 (Sheet 1 of 3)

Mandatory or optional parameters in the ISDN user part messages

THIS TABLE CAN BE FOUND IN FILE NAMED "762T1-E.DOC". IT
HAS TO BE PRINTED IN A3 FORMAT.

IT CONTAINS 3 PAGES.

TABLE Aù2/Q.762

ISDN user part message acronyms



English

 French

 Spanish

 ACM

 ACO

 MDC

 Address complete

 ANM

 REP

 RST

 Answer

 BLA

 BLA

 ARB

 Blocking acknowledgement

 BLO

 BLO

 BLO

 Blocking

 CCR

 CCD

 PPC

 Continuity check request

 CFN

 ICO

 CFN

 Confusion

 CGB

 BLG

 BGC

 Circuit group blocking

 CGBA

 BGA

 ARBG

 Circuit group blocking acknowledge-
ment

 CGU

 DBG

 DGC

 Circuit group unblocking

 CGUA

 DGA

 ARDG

 Circuit group unblocking acknowl-
edgement

 CMC

 MAE

 MLC

 Call modification completed

 CMR

 MAD

 PML

 Call modification request

 CMRJ

 MAR

 RFA

 Call modification reject

 CON

 CON

 CNX

 Connect

 COT

 CCP

 CON

 Continuity

 CPG

 PRG

 PRL

 Call progress

 CRG

 TAX

 TAS

 Charge information

 CQM

 IGD

 IGC

 Circuit group query

 CQR

 IGR

 RIG

 Circuit group query response

 DRS

 LID

 LID

 Delayed release

 FAA

 SUAC

 FAA

 Facility accepted

 FAR

 SUDM

 PFA

 Facility request

 FOT

 IOP

 INT

 Forward transfer

 FRJ

 SURF

 RFA

 Facility reject

 GRA

 RZA

 ARRG

 Circuit group reset acknowledgement

 GRS

 RZG

 RGC

 Circuit group reset

 IAM

 MIA

 MID

 Initial address

 INF

 INF

 INF

 Information

 INR

 IND

 PIN

 Information request

 LPA

 BOA

 AEB

 Loop back acknowledgment

 OLM

 SUR

 SBC

 Overload

 PAM

 FAP

 MDP

 Pass along

 REL

 LIB

 LIB

 Release

 RES

 RPR

 REA

 Resume

 RLC

 LIT

 LIC

 Release complete

 RSC

 RZC

 RCI

 Reset circuit

 SAM

 MSA

 MSD

 Subsequent address

 SUS

 SUS

 SUS

 Suspend

 UBL

 DBO

 DBL

 Unblocking

 UBA

 DBA

 ARD

 Unblocking acknowledgement

 UCIC

 CINE

 CICN

 Unequipped circuit identification
code

 USR

 UAU

 IUU

 Userùtoùuser information