All drawings contained in this Recommendation have been done in Autocad.
Recommendation Q.763
FORMATS AND CODES
1	General
	ISDN user part messages are carried on the signalling link by means of signal units the format of which is described in Recommendation Q.703, § 2.2.
	The format of and the codes used in the service information octet are described in Recommendation Q.704, § 14.2. The service indicator for the ISDN user part is coded 0101.
	The signalling information field of each message signal unit containing an ISDN user part message consists of an integral number of octets and encompasses the following parts (see Figure 1/Q.763):
a)	routing label;
b)	circuit identification code;
c)	message type code;
d)	the mandatory fixed part;
e)	the mandatory variable part;
f)	the optional part, which may contain fixed length and variable length parameter fields.
	Note – The service information octet, the routing label and circuit identification code are not included in the SCCP user data parameter transferred between the ISDN user part and signalling connection control part.
	A description of the various message parts is given in the following sections.
Figure 1/Q.763 - CCITT 73280

1.1	Routing label
	The format and codes used for the routing label are described in Recommendation Q.704, § 2.2. For each individual circuit connection, the same routing label must be used for each message that is transmitted for that connection.
1.2	Circuit identification code
	The format of the circuit identification code (CIC) is shown in Figure 2/Q.763.
Figure 2/Q.763 - CCITT 73290

	The allocation of circuit identification codes to individual circuits is determined by bilateral agreement and/or in accordance with applicable predetermined rules.
	For international applications, the four spare bits of the circuit identification field are reserved for CIC extension, provided that bilateral agreement is obtained before any increase in size is performed. For national applications, the four spare bits can be used as required.
	Allocations for certain applications are defined below:
a)	2048 kbit/s digital path
	For circuits which are derived from a 2048 kbit/s digital path (Recommendations G.732 and G.734) the circuit identification code contains in the 5 least significant bits a binary representation of the actual number of the time slot which is assigned to the communication path.
	The remaining bits in the circuit identification code are used, where necessary, to identify these circuits uniquely among all other circuits of other systems interconnecting an originating and destination point.
b)	8448 kbit/s digital path
	For circuits which are derived from a 8448 kbit/s digital path (Recommendations G.744 and G.747) the circuit identification code contains in the 7 least significant bits an identfication of the circuit which is assigned to the communication path. The codes in Table 1/Q.763 are used.
	The remaining bits in the circuit identification code are used, where necessary, to identify these circuits uniquely among all other circuits of other systems interconnecting an originating and destination point.
c)	Frequency division multiplex (FDM) systems in networks using the 2048 kbit/s pulse code modulation standard
	For frequency division multiplex systems existing in networks that also use the 2048 kbit/s pulse code modulation standard, the circuit identification code contains in the 6 least significant bits the identification of a circuit within a group of 60 circuits carried by 5 basic frequency division multiplex groups which may or may not be part of the same supergroup. The codes in Table 2/Q.763 are used.
	The remaining bits in the circuit identification code are used, where necessary, to identify these circuits uniquely among all other circuits of other systems interconnecting an originating and destination point.
TABLE 1/Q.763
0 0 0 0 0 0 0	 Circuit 1  	
 0 0 0 0 0 0 1	 Circuit 2  	
|	|	
 0 0 1 1 1 1 1	 Circuit 32 	
 0 1 0 0 0 0 0	 Circuit 33 	
|	|	
 1 1 1 1 1 1 0	 Circuit 127	
 1 1 1 1 1 1 1	 Circuit 128	
TABLE 2/Q.763
0 0 0 0 0 0	Unallocated		
0 0 0 0 0 1 
|
 0 0 1 1 0 0	Circuit 1
|
Circuit 12	 1st basic (FDM) group	
0 0 1 1 0 1
0 0 1 1 1 0
0 0 1 1 1 1
0 1 0 0 0 0
0 1 0 0 0 1
|
0 1 1 0 0 1	Circuit 1
Circuit 2
Circuit 3
Unallocated
Circuit 4
|
Circuit 12	 2nd basic (FDM) group	
0 1 1 0 1 0
|
0 1 1 1 1 1 
1 0 0 0 0 0 
1 0 0 0 0 1
|
1 0 0 1 1 0	Circuit 1
|
Circuit 6
Unallocated
Circuit 7
|
Circuit 12	 3rd basic (FDM) group	
1 0 0 1 1 1 
|
1 0 1 1 1 1 
1 1 0 0 0 0 
1 1 0 0 0 1
1 1 0 0 1 0 
1 1 0 0 1 1	Circuit 1
|
Circuit 9
Unallocated
Circuit 10
Circuit 11
Circuit 12	 4th basic (FDM) group	
 1 1 0 1 0 0
|
1 1 1 1 1 1	Circuit 1
|
Circuit 12	5th basic (FDM) group	

1.3	Message type code
	The message type code consists of a one octet field and is mandatory for all messages. The message type code uniquely defines the function and format of each ISDN user part message.
	The allocation with reference to the appropriate descriptive section of this Recommendation is summarized in Table 3/Q.763.
1.4	Formatting principles
	Each message consists of a number of PARAMETERS listed and described in § 2. Each parameter has a NAME which is coded as a single octet (see Table 4/Q.763). The length of a parameter may be fixed or variable, and a LENGTH INDICATOR of one octet for each parameter may be included as described below.
	The detailed format is uniquely defined for each message type as described in § 3.
	A general format diagram is shown in Figure 3/Q.763.
1.5	Mandatory fixed part
	Those parameters that are mandatory and of fixed length for a particular message type will be contained in the mandatory fixed part. The position, length and order of the parameters is uniquely defined by the message type, thus the names of the parameters and the length indicators are not included in the message.
1.6	Mandatory variable part
	Mandatory parameters of variable length will be included in the mandatory variable part. Pointers are used to indicate the beginning of each parameter. Each pointer is encoded as a single octet. The name of each parameter and the order in which the pointers are sent is implicit in the message type. Parameter names are, therefore, not included in the message. The details of how pointers are encoded is found in § 2.3. The number of parameters, and thus the number of pointers is uniquely defined by the message type.
	A pointer is also included to indicate the beginning of the optional part. If the message type indicates that no optional part is allowed, then this pointer will not be present. If the message type indicates that an optional part is possible, but there is no optional part included in this particular message than a pointer field containing all zeros will be used. It is recommended that all future message types with a mandatory variable part indicate that an optional part is allowed.
	All the pointers are sent consecutively at the beginning of the mandatory variable part. Each parameter contains the parameter length indicator followed by the contents of the parameters.
1.7	Optional part
	The optional part consists of parameters that may or may not occur in any particular message type. Both fixed length and variable length parameters may be included. Optional parameters may be transmitted in any order. Each optional parameter will include the parameter name (one octet) and the length indicator (one octet) followed by the parameter contents.
1.8	End of optional parameters octet
	If optional parameters are present and after all optional parameters have been sent, an “end of optional parameters” octet containing all zeros will be transmitted.
1.9	Order of transmission
	Since all the fields consist of an integral number of octets, the formats are presented as a stack of octets. The first octet transmitted is the one shown at the top of the stack and the last is the one at the bottom (see Figure 3/Q.763).
	Unless otherwise indicated, within each octet and subfield the bits are transmitted with the least significant bit first.
1.10	Coding of spare bits
	Spare bits are coded 0 unless indicated otherwise.
Figure 3/Q.763 - CCITT 73070

1.11	National message types and parameters
	If message type codes and parameter name codes are required for national uses not included in this Recommendation, the codes chosen should be from the highest code downwards, that is, starting at code 11111111. Codes in the range 11111111 to 11100000 are reserved exclusively for this purpose.
2	Parameter formats and codes
2.1	Message type codes
	The encoding of the message type is shown in Table 3/Q.763.
TABLE 3/Q.763
Message type	 Reference (Table)	 Code	
 Address complete	  5/Q.763	 00000110	
 Answer	  6/Q.763	 00001001	
 Blocking	 23/Q.763	 00010011	
 Blocking acknowledgement	 23/Q.763	 00010101	
 Call modification completed	 24/Q.763	 00011101	
 Call modification request	 24/Q.763	 00011100	
 Call modification reject	 24/Q.763	 00011110	
 Call progress	  7/Q.763	 00101100	
 Circuit group blocking	 25/Q.763	 00011000	
 Circuit group blocking acknowledgement	 25/Q.763	 00011010	
 Circuit group query	 26/Q.763	 00101010	
 Circuit group query response	  8/Q.763	 00101011	
 Circuit group reset	 26/Q.763	 00010111	
 Circuit group reset acknowledgement	  9/Q.763	 00101001	
 Circuit group unblocking	 25/Q.763	 00011001	
 Circuit group unblocking acknowledgement	 25/Q.763	 00011011	
 Charge information a)	 (see Note)	 00110001	
 Confusion	 10/Q.763	 00101111	
 Connect	 11/Q.763	 00000111	
 Continuity	 12/Q.763	 00000101	
 Continuity check request	 23/Q.763	 00010001	
 Delayed release a)	 21/Q.763	 00100111	
 Facility accepted	 27/Q.763	 00100000	
 Facility reject	 13/Q.763	 00100001	
 Facility request	 27/Q.763	 00011111	
 Forward transfer	 21/Q.763	 00001000	
 Information	 14/Q.763	 00000100	
 Information request	 15/Q.763	 00000011	
 Initial address	 16/Q.763	 00000001	
 Loop back acknowledgement a)	 23/Q.763	 00100100	
 Overload a)	 23/Q.763	 00110000	
 Pass–along	 28/Q.763	 00101000	
 Release	 17/Q.763	 00001100	
 Release complete	 18/Q.763	 00010000	
 Reset circuit	 23/Q.763	 00010010	
 Resume	 22/Q.763	 00001110	
 Subsequent address	 19/Q.763	 00000010	
 Suspend	 22/Q.763	 00001101	
 Unblocking	 23/Q.763	 00010100	
 Unblocking acknowledgement	 23/Q.763	 00010110	
 Unequipped CIC a)	 23/Q.763	 00101110	
 User–to–user information	 20/Q.763	 00101101	
Reserved (used in 1984 version)		00001010 00001011 00001111 00100010 00100011 00100101 00100110	
 a) For national use only
Note – The format of this message is a national matter.
2.2	Coding of the length indicator
	The length indicator field is binary coded to indicate the number of octets in the parameter content field. The length indicated does not include the parameter name octet or the length indicator octet.
2.3	Coding of the pointers
	The pointer value (in binary) gives the number of octets between the pointer itself (included) and the first octet (not included) of the parameter associated with that pointer.
	The pointer value all zeros is used to indicate that, in the case of optional parameters, no optional parameter is present.
3	ISDN user part parameters
3.1	Parameter names
	The parameter name codes are given in Table 4/Q.763 together with references to the subsections in which they are described.
3.2	Access transport
	The format of the access transport parameter field is shown in Figure 4/Q.763.
Figure 4/Q.763 - T1110030-88

	The information element is coded as described in Recommendation Q.931, § 4.5. Multiple Q.931 information elements can be included within the access transport parameter. The information elements applicable to a particular usage of the access transport parameter are dependent on, and will be determined by, the relevant procedures.
3.3	Automatic congestion level
	The format of the automatic congestion level parameter field is shown in Figure 5/Q.763.
Figure 5/Q.763 - T1110040-88

TABLE 4/Q.763
Parameter name	 Reference (§)	 Code	
 Access transport	 3.2 	 00000011	
 Automatic congestion level	 3.3 	 00100111	
 Backward call indicators	 3.4 	 00010001	
 Call modification indicators	 3.5 	 00010111	
 Call reference	 3.6 	 00000001	
 Called party number	 3.7 	 00000100	
 Calling party number	 3.8 	 00001010	
 Calling party's category	 3.9 	 00001001	
 Cause indicators	 3.10	 00010010	
 Circuit group supervision message type indicator	 3.11	 00010101	
 Circuit state indicator	 3.12	 00100110	
 Closed user group interlock code	 3.13	 00011010	
 Connected number	 3.14	 00100001	
 Connection request	 3.15	 00001101	
 Continuity indicators	 3.16	 00010000	
 End of optional parameters	 3.17	 00000000	
 Event information	 3.18	 00100100	
 Facility indicator	 3.19	 00011000	
 Forward call indicators	 3.20	 00000111	
 Information indicators	 3.21	 00001111	
 Information request indicators	 3.22	 00001110	
 Nature of connection indicators	 3.23	 00000110	
 Optional backward call indicators	 3.24	 00101001	
 Optional forward call indicators	 3.25	 00001000	
 Original called number	 3.26	 00101000	
 Range and status	 3.27	 00010110	
 Redirecting number	 3.28	 00001011	
 Redirection information	 3.29	 00010011	
 Redirection number	 3.30	 00001100	
 Signalling point code a)	 3.31	 00011110	
 Subsequent number	 3.32	 00000101	
 Suspend/Resume indicators	 3.33	 00100010	
 Transit network selection a)	 3.34	 00100011	
 Transmission medium requirement	 3.35	 00000010	
 User service information	 3.36	 00011101	
 User–to–user indicators	 3.37	 00101010	
 User–to–user information	 3.38	 00100000	
 Reserved (used in 1984 version, Red Book)		00010100 00011001 00011011 00011100 00011111	
 Reserved for multi–slot identifier		00100101	
 a)  For national use only

	The following codes are used in the automatic congestion level parameter field:
00000000		spare
00000001		congestion level 1 exceeded
00000010		congestion level 2 exceeded
00000011	ü	
  to			ý	spare
11111111	þ	
3.4	Backward call indicators
	The format of the backward call indicators parameter field is shown in Figure 6/Q.763.
Figure 6/Q.763 - CCITT 73375

	The following codes are used in the backward call indicators parameter field:
bits	B	A:	Charge indicator
0	0	no indication
0	1	no charge
1	0	charge
1	1	spare
bits	D	C:	Called party's status indicator
0	0	no indication
0	1	subscriber free
1	0	connect when free
1	1	spare
bits	F	E:	Called party's category indicator
0	0	no indication
0	1	ordinary subscriber
1	0	payphone
1	1	spare
bits	H	G:	End–to–end method indicator (Note)
0	0	no end–to–end method available (only link–by–link method available)
0	1	pass along method available
1	0	SCCP method available
1	1	pass along and SCCP methods available
bit	I:		Interworking indicator (Note)
0		no interworking encountered
1		interworking encountered
bit	J:		End–to–end information indicator (Note)
0		no end–to–end information available
1		end–to–end information available
bit	K:		ISDN User Part indicator (Note)
0		ISDN User Part not used all the way
1		ISDN User Part used all the way
bit	L:		Holding indicator (national use)
0		holding not requested
1		holding requested
bit	M:		ISDN access indicator
0		terminating access non–ISDN
1		terminating access ISDN
bit	N:		Echo control device indicator
0		incoming half echo control device not included
1		incoming half echo control device included
bits	P	O:	SCCP method indicator
0	0	no indication
0	1	connectionless method available
1	0	connection oriented method available
1	1	connectionless and connection oriented methods available
	Note – Bits G–K and O–P constitute the protocol control indicator.
3.5	Call modification indicators
	The format of the call modification indicators parameter field is shown in Figure 7/Q.763.
Figure 7/Q.763 - CCITT 73370

	The following codes are used in the call modification indicators parameter field:
bits	B	A:	Modification indicator
0	0	spare
0	1	modify to service 1
1	0	modify to service 2
1	1	spare
bits	H	C:	Spare
	Note – Service 1 and 2 are described by the transmission medium requirement.
3.6	Call reference
	The format of the call reference parameter is shown in Figure 8/Q.763.
Figure 8/Q.763 - T1121550-89

	The following codes are used in the subfields of the call reference parameter field:
a)	Call identity
A code expressing in pure binary representation the identification number allocated to the call.
b)	Point code
The code of the signalling point in which the call identity is relevant.
3.7	Called party number
	The format of the called party number parameter field is shown in Figure 9/Q.763.
Figure 9/Q.763 - T1110050-88

	The following codes are used in the subfields of the called party number parameter field:
a)	Odd/even indicator
0	even number of address signals
1	odd number of address signals
b)	Nature of address indicator
0000000		spare
0000001		subscriber number
0000010		spare, reserved for national use
0000011		national (significant) number
0000100		international number
0000101	ü
  to		ý	spare
1101111	þ
1110000	ü
  to		ý	reserved for national use
1111110	þ
1111111		spare
c)	Internal network number indicator (INN ind.)
0	routing to internal network number allowed
1	routing to internal network number not allowed

d)	Numbering plan indicator
000	spare
001	ISDN (Telephony) numbering plan (Recommandation E.164, E.163)
010	spare
011	Data numbering plan (Recommandation X.121)
100	Telex numbering plan (Recommendation F.69)
101	reserved for national use
110	reserved for national use
111	spare
e)	Address singal
0000	digit 0
0001	digit 1
0010	digit 2
0011	digit 3
0100	digit 4
0101	digit 5
0110	digit 6
0111	digit 7
1000	digit 8
1001	digit 9
1010	spare
1011	code 11
1100	code 12
1101	spare
1110	spare
1111	ST
	The most significant address signal is sent first. Subsequent address signals are sent in successive 4–bit fields.
f)	Filler
In case of an odd number of address signals, the filler code 0000 is inserted after the last address signal.
3.8	Calling party number
	The format of the calling party number parameter field is shown in Figure 10/Q.763.
Figure 10/Q.763 - T1110060-88

	The following codes are used in the calling party number parameter field.
a)	Odd/even indicator:
See § 3.7 a).
b)	Nature of address indicator
0000000		spare
0000001		subscriber number
0000010		spare, reserved for national use
0000011		national (significant) number
0000100		international number
0000101	ü
  to		ý	spare
1101111	þ
1110000	ü
  to		ý	reserved for national use
1111110	þ
1111111		spare
Note – Other types of nature of address indications (e.g. transit exchange identity) are for further study.
c)	Calling party number incomplete indicator (NI)
0	complete
1	incomplete
d)	Numbering plan indicator
See § 3.7 d).
e)	Address presentation restricted (Pres. Restric.) indicator
00	presentation allowed
01	presentation restricted
10	address not available (Note)
11	spare
Note – When the address is unavailable, the subfields in items a), b), c) and d) are coded with 0's.
f)	Sceening indicator
00	reserved (Note)
01	user provided, verified and passed
10	reserved (Note)
11	network provided
	Note – Code 00 and 10 are reserved for “user provided, not verified” and “user provided, verified and failed” respectively.
g)	Address signal
0000		digit 0
0001		digit 1
0010		digit 2
0011		digit 3
0100		digit 4
0101		digit 5
0110		digit 6
0111		digit 7
1000		digit 8
1001		digit 9
1010		spare
1111		code 11
1100		code 12
1101	ü
 to		ý	spare
1111	þ
h)	Filler
See § 3.7 f).
3.9	Calling party's category
	The format of the calling party's category parameter field is shown in Figure 11/Q.763.
Figure 11/Q.763 - CCITT 73380

	The following codes are used in the calling party's category parameter field.
00000000		calling party's category unknown at this time
00000001		operator, language French
00000010		operator, language English
00000011		operator, language German
00000100		operator, language Russian
00000101		operator, language Spanish
00000110	ü	available to Administrations for
00000111	ý	selecting a particular language
00001000	þ	by mutual agreement
00001001		reserved (see Recommendation Q.104) (Note)
00001010		ordinary calling subscriber
00001011		calling subscriber with priority
00001100		data call (voice band data)
00001101		test call
00001110		spare
00001111		payphone
00010000	ü
  to			ý	spare
11011111	þ
11100000	ü
  to			ý	reserved for national use
11111110	þ
11111111		spare
	Note – In national networks code 00001001 may be used to indicate that the calling party is a national operator.
3.10	Cause indicators
	The format of the cause indicators parameter field is shown in Figure 12/Q.763.
Figure 12/Q.763 - T1110070-88

	The following codes are used in the subfields of the cause indicators parameter field:
a)	Extension indicator (ext)
0	octet continues through the next octet (e.g. octet 1 to 1a)
1	last octet
b)	Coding standard
00	CCITT standard, as described below
01	reserved for other international standards (Note)
10	national standard (Note)
11	standard specific to identified location (Note)
	Note – These other coding standards should be used only when the desired cause cannot be represented with the CCITT standard.
c)	Location
0000	user
0001	private network serving the local user
0010	public network serving the local user
0011	transit network
0100	public network serving the remote user
0101	private network serving the remote user
0111	international network
1010	beyond an interworking point, all other values are reserved.
	Note – Depending on the location of the users, the public network serving the local user may be the same network serving the remote user. Rules for coding the location field are defined in Recommendation Q.931 Annex J.
d)	Recommendation
0000000	Rec. Q.763
0000011	Rec. X.21
0000100	Rec. X.25
0000101	Public land mobile networks, Q.1000 Series.
	All other values are reserved.
Note – If octet 1a is omitted, Recommendation Q.763 is assumed.
e)	Cause value
	The cause value is divided into two fields, a class (bits 5 through 7) and a value within a class (bits 1 through 4). The decimal equivalent of the cause value is shown in brackets beside the cause value.
Class 000 and 001 – normal event:
0000001	(1)	unallocated (unassigned) number
0000010	(2)	no route to specified transit network (national use)
0000011	(3)	no route to destination
0000100	(4)	send special information tone
0000101	(5)	misdialled trunk prefix
0010000	(16)	normal call clearing
0010001	(17)	user busy
0010010	(18)	no user responding
0010011	(19)	no answer from user (user alerted)
0010101	(21)	call rejected
0010110	(22)	number changed
0011011	(27)	destination out of order
0011100	(28)	address incomplete
0011101	(29)	facility rejected
0011111	(31)	normal – unspecified
Class 010 – resource unavailable:
0100010	(34)	no circuit available
0100110	(38)	network out of order
0101001	(41)	temporary failure
0101010	(42)	switching equipment congestion
0101100	(44)	requested channel not available
0101111	(47)	resource unavailable – unspecified
Class 011 – service or option not available:
0110010	(50)	requested facility not subscribed
0110111	(55)	incoming calls barred within CUG
0111001	(57)	bearer capability not authorized
0111010	(58)	bearer capability not presently available
0111111	(63)	service/option not available – unspecified
Class 100 – service or option not implemented:
1000001	(65)	bearer capability not implemented
1000101	(69)	requested facility not implemented
1000110	(70)	only restricted digital information bearer capability is available
1001111	(79)	service or option not implemented – unspecified
Class 101 – invalid mesage (e.g. parameter out of range):
1010111	(87)	called user not member of CUG
1011000	(88)	incompatible destination
1011011	(91)	invalid transit network selection (national use)
1011111	(95)	invalid message – unspecified
Class 110 – protocol error (e.g. unknown message):
1100001	(97)	message type non–existant or not implemented
1100011	(99)	parameter non–existant or not implemented – discarded
1100101	(103)	parameter non–existent or not implemented – passed on
1101111	(111)	protocol error – unspecified
Class 111 – interworking:
1111111	(127)	interworking unspecified

f)	Diagnostic
	The format and existence of the diagnostic field is dependant on the cause value and the location of generation. For causes generated by a public network, the following diagnostics may be included:
Cause	Diagnostic	Format	
  1	Condition	See below	
  2	Transit Network identity	See § 3.34 (Note)	
  3	Condition	See below	
 16	Condition	See below	
 21	Condition	See below	
 22	Called party number (new)	See § 3.7 (Note)	
 29	Rejected parameter (Note)		
 50	Rejected parameter (Note)		
 57	Attribute identity	See below	
 58	Attribute identity	See below	
 65	Attribute identity	See below	
 69	Rejected parameter (Note)		
 97	Message type	See Table 3/Q.763	
 99	Parameter name(s)	See Table 4/Q.763	
103	Parameter name(s)	See Table 4/Q.763	
Note – These diagnostics shall also include the parameter name and length octets.
1)	Diagnostic with attribute identity
	The format of the diagnostic field when coded with an attribute identity is shown in Figure 13/Q.763.
Figure 13/Q.763 - T1110080-88

The attribute number subfield identifies the rejected attribute as follows:
0110001	Information transfer capability
0110010	Information transfer mode
0110011	Information transfer rate
0110100	Structure
0110101	Configuration
0110110	Etablishment
0110111	Symmetry
0111000	Information transfer rate (dest to orig)
0111001	Layer identification and corresponding user information
	The rejected attribute and available attribute subfields are coded the same as in the equivalent octet of the user service information parameter field (see § 3.36) which contains the relevant attribute. Bits not related to the rejected attribute are coded 0. If more than one bearer capability attribute was rejected, the diagnostic field can be repeated.
	The extension bit (ext), when coded 0, indicates that this diagnostic continues to the next octet (e.g. octet 3a to 3b). The inclusion of the available attribute subfield is optional.

2)	Condition diagnostic
	A condition diagnostic is a 1 octet field containing an extension bit (bit 8) and one of the following codes in bits 2–1:
00	unknown
01	permanent
10	transient
11	spare
Bits 3 to 7 of a condition diagnostic are spare.
3.11	Circuit group supervision message type indicator
	The format of the circuit group supervision message type indicator parameter field is shown in Figure 14/Q.763.
Figure 14/Q.763 - CCITT 73370

	The following codes are used in the circuit group supervision message type indicator parameter field:
bits	B	A:	Type indicator
0	0	maintenance oriented
0	1	hardward failure oriented
1	0	reserved for national use (used in 1984 version)
1	1	spare
bits	C	H:	Spare
3.12	Circuit state indicator
	The format of the circuit state indicator parameter field is shown in Figure 15/Q.763.
figure 15/Q.763 - T1110090-88

	The number of octets in the circuit state indicator parameter field is equal to the specified range + 1. Each circuit state indicator octet is associated with a circuit identification code such that octet n is associated with circuit identification code m+n–1, where m is the circuit identification code contained in the message.
	The following codes are used in each circuit state indicator octet.
a)	for bits D C = 0 0
bits	B	A:	Maintenance blocking state
0	0	transient
0	1	spare
1	0	spare
1	1	unequipped
bits	E–H:	Spare
b)	for bits D C not equal to 0 0
bits	B	A:	Maintenance blocking state
0	0	no blocking (active)
0	1	locally blocked
1	0	remotely blocked
1	1	locally and remotely blocked
bits	D	C:	Call processing state
0	1	circuit incoming busy
1	0	circuit outgoing busy
1	1	idle
bits	F	E:	Hardware blocking state (Note)
0	0	no blocking (active)
0	1	locally blocked
1	0	remotely blocked
1	1	locally and remotely blocked
bits	G–H:	Spare
Note – If bits F E are not coded 0 0, bits D C must be coded 1 1.
3.13	Closed user group interlock code
	The format of the closed user group interlock code parameter field is shown in Figure 16/Q.763.
Figure 16/Q.763 - T1110100-88

	The following codes are used in the subfields of the closed user group interlock code parameter field:
a)	Network identity (NI) (octets 1 and 2)
Each digit is coded in the binary coded decimal representation from 0 to 9.
	If the first digit of this field is coded 0 or 9, the TCC (Telephony Country Code) follows in the second to fourth NI digits (the most significant TCC digit is in the 2nd NI digit). If the TCC is one or two digits long, the excess digit(s) is inserted with the code for RPOA or network identification, if necessary. If octet 2 is not required, it is coded all 0.
Coding of the first digit as 1 or 8 is excluded.
	If the first digit is not 0, 9, 1 or 8 this field contains a DNIC (Data Network Identification Code) as defined in Recommendation X.121.
b)	Binary code (octets 3 and 4)
	A code allocated to a closed user group administered by a particular ISDN or data network. Bit 8 of octet 3 is the most significant and bit 1 of octet 4 is the least significant.
3.14	Connected number
	The format of the connected number parameter field corresponds to the format shown in Figure 17/Q.763.
Figure 17/Q.763 - T1110060-88

	The following codes are used in the subfields of the connected number parameter field:
a)	Odd/even indicator: see § 3.7 a)
b)	Nature of address indicator: see § 3.7 b)
c)	Numbering plan indicator: see § 3.7 d)
d)	Address presentation restricted indicator: see § 3.8 e)
e)	Screening indicator: see § 3.8 f)
f)	Address signal: see § 3.8 g)
g)	Filler: see § 3.7 h).
3.15	Connection request
	The format of the connection request parameter field is shown in Figure 18/Q.763.
	The following codes are used in the subfields of the connection request parameter field:
a)	Local reference
	A code indicating the local reference allocated by the signalling connection control part to the end–to–end connection.
b)	Point code
A code identifying the signalling point at which the connection request originated.
c)	Protocol class
	A code identifying in pure binary representation, the protocol class requested for the end–to–end connection.
d)	Credit
	A code identifying in pure binary representation the window size requested for the end–to–end connection.
Figure 18/Q.763 - CCITT 73351

3.16	Continuity indicators
	The format of the continuity indicators parameter field is shown in Figure 19/Q.763.
Figure 19/Q.763 - CCITT 73370

	The following codes are used in the continuity indicators parameter field.
bit	A:		Continuity indicator
0		continuity check failed
1		continuity check successful
bits	B–H:	Spare
3.17	End of optional parameters indicator
	The last optional parameter field of a message is followed by the end of optional parameters indicator, which occupies a one octet field containing all zeros.
3.18	Event information
	The format of the event information parameter field is shown in Figure 20/Q.763.

Figure 20/Q.763 - CCITT73370

	The following codes are used in the event indicator parameter field:
bits	GFEDCBA:	Event indicator
0000000		spare
0000001		ALERTING
0000010		PROGRESS
0000011		in–band information of an appropriate pattern is now available
0000100		call forwarded on busy
0000101		call forwarded on no reply
0000110		call forwarded unconditional
0000111	ü
  to		ý	spare
1111111	þ
bit	H:	Event presentation restricted indicator
0	no indication
1	presentation restricted
3.19	Facility indicator
	The format of the facility indicator parameter field is shown in Figure 21/Q.763.
Figure 21/Q.763 - CCITT 73380

	The following codes are used in the facility indicator parameter field.
00000000		spare
00000001		spare
00000010		user–to–user service
00000011	ü
  to			ý	spare
11111111	þ
3.20	Forward call indicators
	The format of the forward call indicators parameter field is shown in Figure 22/Q.763.
Figure 22/Q.763 - CCITT 73375

	The following codes are used in the forward call indicators parameter field:
bit	A:		National/international call indicator
0		call to be treated as a national call
1		call to be treated as an international call
	This bit can be set to any value in the country of origin. In the international network this bit is not checked. In the destination country, calls from the international network will have this bit set to 1.
bits	C	B:	End–to–end method indicator (Note)
0	0	no end–to–end method available (only link–by–link method available)
0	1	pass along method available
1	0	SCCP method available
1	1	pass along and SCCP methods available
bit	D:		Interworking indicator (Note)
0		no interworking encountered (No. 7 signalling all the way)
1		interworking encountered
bit	E:		End–to–end information indicator (Note)
0		no end–to–end information available
1		end–to–end information available
bit	F:		ISDN user part indicator (Note)
0		ISDN user part not used all the way
1		ISDN user part used all the way
bits	H	G:	ISDN user part preference indicator
0	0	ISDN user part preferred all the way
0	1	ISDN user part not required all the way
1	0	ISDN user part required all the way
1	1	spare
bit	I:		ISDN access indicator
0		originating access non–ISDN
1		originating access ISDN
bits	K	J:	SCCP method indicator
0	0	no indication
0	1	connectionless method available
1	0	connection oriented method available
1	1	connectionless and connection oriented methods available
bit	L:		Spare
bits	M–P:	Reserved for national use
	Note – Bits B–F and J–K constitute the protocol control indicator.
3.21	Information indicators
	The format of the information indicators parameter field is shown in Figure 23/Q.763.
Figure 23/Q.763 - CCITT 73375

	The following codes are used in the information indicators parameter field:
bits	B	A:	Calling party address response indicator
0	0	calling party address not included
0	1	calling party address not available
1	0	spare
1	1	calling party address included
bit	C:		Hold provided indicator (national use)
0		hold not provided
1		hold provided
bits	E	D:	Spare
bit	F:		Calling party's category response indicator
0		calling party's category not included
1		calling party's category included
bit	G:		Charge information response indicator (national use)
0		charge information not included
1		charge information included
bit	H:		Solicited information indicator
0		solicited
1		unsolicited
bits	I–P:	Spare
3.22	Information request indicators
	The format of the information request indicators parameter field is shown in Figure 24/Q.763.
Figure 24/Q.763 - CCITT 73375

	The following codes are used in the information request indicators parameter field.
bit	A:		Calling party address request indicator
0		calling party address not requested
1		calling party address requested
bit	B:		Holding indicator (national use)
0		holding not requested
1		holding requested
bit	C:		Spare
bit	D:		Calling party's category request indicator
0		calling party's category not requested
1		calling party's category requested
bit	E:		Charge information request indicator (national use)
0		charge information not requested
1		charge information requested
bits	G	F:	Spare
bit	H:		Malicious call identification request indicator (national use)
0		malicious call identification not requested
1		malicious call identification requested
bits	I–P:	Spare
3.23	Nature of connection indicators
	The format of the nature of connection indicators parameter field is shown in Figure 25/Q.763.
Figure 25/Q.763 - CCITT 73380

	The following codes are used in the nature of connection indicators parameter field:
bits	B	A:	Satellite indicator
0	0	no satellite circuit in the connection
0	1	one satellite circuit in the connection
1	0	two satellite circuits in the connection
1	1	spare
bits	D	C:	Continuity check indicator
0	0	continuity check not required
0	1	continuity check required on this circuit
1	0	continuity check performed on a previous circuit
1	1	spare
bit	E:		Echo control device indicator
0		outgoing half echo control device not included
1		outgoing half echo control device included
bits	F–H:	Spare
3.24	Optional backward call indicators
	The format of the optional backward call indicators parameter field is shown in Figure 26/Q.763.