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.nr LL 40.5P
.nr ll 40.5P
.nr HM 3P
.nr FM 6P
.nr PO 4P
.nr PD 9p
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.rs
\v | 5i'
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation T.30)
.sp 9p
.RT
.ce 0
.ce 1000
\fBProcedure for G3 document facsimile transmission in the general\fR 
.sp 1P
.RT
.ce 0
.ce 1000
\fBswitched telephone network incorporating error correction\fR 
.ce 0
.LP
A.1
	\fIIntroduction\fR 
.sp 1P
.RT
.PP
A.1.1 
This Annex is intended to apply to document facsimile apparatus
covered by Recommendation\ T.4, Annex\ A. It describes the procedures and 
signals to be used where facsimile equipment incorporates error correction 
capabilities. When existing equipment is operating in a non\(hyCCITT manner, 
they shall not interfere with equipment operating in accordance with the 
Series\ T 
Recommendation.
.sp 9p
.RT
.PP
A.1.2 
Use of this Annex is optional
.sp 9p
.RT
.sp 1P
.LP
A.1.3
	\fIOutline of the\fR 
\fIerror correction method\fR 
.sp 9p
.RT
.PP
The error correction method described in this Annex is based on
the half\(hyduplex page selective repeat ARQ (automatic repeat request)
technique.
.PP
An HDLC frame structure is utilized for all binary coded facsimile
message procedures.
.PP
The transmitting terminal can decide to use either 256 or 64 octets
for the frame size by using DCS command. The receiving terminal must be 
able to receive 256\ and 64\ octets of frame size. 
.PP
The transmitting station divides the coded data specified in
Recommendation\ T.4, \(sc\ 4 into a number of frames and transmits them 
with each 
frame number.
.PP
When the previous message has not been satisfactorily received, the
receiving station transmits PPR response to indicate that the frames specified 
in the associated facsimile information field are required to be 
retransmitted.
.PP
When PPR is received, the transmitting station retransmits the
requested frames specified in PPR information field.
.PP
When PPR is received four times for the same block, either the EOR
command is transmitted for end of retransmission or CTC (continue to correct) 
command is sent for continuous retransmission. 
.PP
In the case of continuous retransmission, the modem speed may fall
back or continue at the same speed in accordance with the decision of the
transmitting terminal.
.RT
.sp 2P
.LP
A.2
	\fIDefinitions\fR 
.sp 1P
.RT
.PP
A.2.1 
The signals and definitions used in the error correction
procedure are as defined in the main body of this Recommendation unless
specified otherwise.
.sp 9p
.RT
.PP
A.2.2 
Frame formats of RCP frame and FCD frame for the in\(hymessage
procedure are defined in Recommendation\ T.4, Annex\ A.
.sp 9p
.RT
.sp 1P
.LP
A.2.3
	\fIRelations between a page, blocks, partial pages and frames\fR 
.sp 9p
.RT
.PP
One page of coded data as specified in Recommendation T.4, \(sc\ 4 is divided 
into a number of blocks. The block contains a number of frames. A 
partial page is defined as one transmitted block or a number of retransmitted 
frames. 
.RT
.sp 1P
.LP
A.2.4
	\fIBlock size\fR 
.sp 9p
.RT
.PP
The block size is defined as the maximum number of frames that can be sent 
by the transmitter before receiving the response. 
.bp
.RT
.sp 2P
.LP
A.3
	\fIBlock size and frame size\fR 
.sp 1P
.RT
.PP
A.3.1 
For T.4 error correction mode, a transmitting terminal
indicates frame size by using DCS signal.
.sp 9p
.RT
.PP
A.3.2
The following values of frame size are applicable: 256 or 64
octets. These values of frame size do not include either FCF or frame
number octet. Therefore, the total length of the HDLC information field
including both the FCF and the frame number octet is as follows: 258\ or
66\ octets.
.PP
A.3.3
The receiving terminal must have the following condition:
.LP
	frame size: 256 or 64 octets.
.LP
	block size: 256 frames.
.PP
A.3.4
The transmitting terminal may send the block whose size is less
than 256\ frames at the end of each page. This block is called a 
short
block
.
.PP
A.3.5
The frame size should not be changed during a transmission of
one page. In order to change the frame size, indication of mode change 
should be made using PPS | (mu | OM or EOR | (mu | OM command at the page 
boundary. 
.sp 2P
.LP
A.4
	\fIInformation field\fR  | (see also \(sc\ 5.3.6)
.sp 1P
.RT
.PP
The HDLC information field is of variable length and contains
the specific information for the control and message interchange between two
facsimile stations. In this Recommendation it is divided into two parts, the
facsimile control field (FCF) and the facsimile information field
(FIF).
.RT
.LP
	1)
	\fIFacsimile control field (FCF)\fR \ \(em\ The facsimile
control field is defined to be the first 8 bits or
16\ bits of the HDLC information field. FCF of 16\ bits should be
applied only for the optional\ T.4 error correction mode. This
field contains the complete information regarding the type of
information being exchanged and the position in the overall
sequence. The bit assignments within the FCF are as follows:
.LP
	Where X appears as the first bit of FCF, X will be defined
as follows:
.LP
	\(em
	X\ \ is set to 1 by the station which receives a valid
DIS signal;
.LP
	\(em
	X\ \ is set to 0 by the station which receives a valid
and appropriate response to a DIS signal;
.LP
	\(em
	 X\ \ will remain unchanged until the station again enters the beginning 
of phase\ B. 
.LP
	2)
	\fIFacsimile information field (FIF)\fR \ \(em\ In many cases
the FCF will be followed by the transmission of
additional 8\(hybit octets to further clarify the facsimile
procedure. This information for the basic binary coded system
would consist of the definition of the information in DIS, DCS,
DTC, CSI, CIG, TSI, NSC, NSF, NSS, CTC, PPS and PPR signals.
.sp 1P
.LP
A.4.1
	\fICommand to receive\fR  | (see also \(sc\ 5.3.6.1.3)
.sp 9p
.RT
.PP
From the transmitter to the receiver.
.PP
Format:\ X100\ XXXX
.RT
.LP
	1)
	\fIContinue to correct (CTC)\fR \ \(em\ This command
indicates that the transmitting station shall continue to correct the previous 
message. (This is a response to the 4th PPR received, and indicates that 
the 
transmitting station shall immediately send the requested frames specified 
in PPR information field.) 
.LP
	When the transmitter receives PPR four times, the modem
speed may fall back or continue the previous transmission speed using CTC
command.
.LP
	This command should have the FIF of 2 octets, which
corresponds to the bits\ No.\ 1\(hy16 of DCS standard command (See Table\ 
2/T.30). 
The receiving terminal uses only the bits\ No.\ 11\(hy14 to determine the data
signalling rate.
.LP
	Format:\ X100\ 1000
.sp 1P
.LP
A.4.2
	\fIPre\(hymessage response signals\fR  | (see also \(sc 5.3.6.1.4)
.sp 9p
.RT
.PP
From the receiver to the transmitter.
.PP
Format:\ X010\ XXXX
.RT
.LP
	1)
	\fIResponse for continue to correct (CTR)\fR \ \(em\ This
signal is the digital response to CTC signal, so that the
receiving terminal can accept the contents included in CTC
signal.
.LP
	Format:\ X010\ 0011
.bp
.sp 1P
.LP
A.4.3
	\fIPost message commands\fR  | (see also \(sc\ 5.3.6.1.6)
.sp 9p
.RT
.PP
From the transmitter to the receiver.
.PP
Format:\ X111\ XXXX
.RT
.LP
	1)
	\fIPartial page signal (PPS)\fR \ \(em\ This command
indicates the end of a partial page or a complete
page of facsimile information and also indicates to return to
the beginning of phase\ B or\ C upon receipt of\ MCF.
.LP
	Format:\ X111\ 1101
.LP
	The frame construction of PPS command and transmission order of
bits included in\ I1\(hyI3 are shown in Figure\ A\(hy1/T.30.
.LP
.rs
.sp 39P
.ad r
\fBFigure A\(hy1/T.30, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
	2)
	\fIEnd of retransmission (EOR)\fR \ \(em\ This command
indicates that the transmitter decides to terminate
the retransmission of error frames in the previous partial page
and to transmit the next block upon receipt of ERR response.
.LP
	Format:\ X111\ 0011
.bp
.LP
	The frame construction of EOR command is shown in
Figure\ A\(hy2/T.30.
.LP
.rs
.sp 19P
.ad r
\fBFigure A\(hy2/T.30, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
	3)
	\fIReceive ready (RR)\fR \ \(em\ This command is used to ask
for the status of the receiver.
.LP
	Format:\ X111\ 0110
.LP
	\fINote\ 1\fR \ \(em\ This command is defined for flow control.
.LP
	\fINote\ 2\fR \ \(em\ For flow control method, make reference to \(sc\ A.5.
.sp 1P
.LP
A.4.4
	\fIPost\(hymessage responses\fR  | (see also \(sc\ 5.3.6.1.7)
.sp 9p
.RT
.PP
From the receiver to the transmitter.
.PP
Format:\ X011\ XXXX
.RT
.LP
	1)
	\fIPartial page request (PPR)\fR \ \(em\ This signal
indicates that the previous message has not been
satisfactorily received and that the frames specified in the
associated facsimile information field are required to be
retransmitted.
.LP
	Format:\ X011\ 1101
.PP
The facsimile information field of the PPR signal is a fixed
length of 256\ bits, each bit corresponds to an FCD frame i.e., the first 
bit to the first frame\ etc. For FCD frames which are received correctly, 
the 
corresponding bit in the PPR information field will be set to\ \*Q0\*U; 
those that are received incorrectly or not received will have their bit 
set to\ \*Q1\*U. 
.PP
If more than one PPR signal is transmitted, the bit corresponding to an 
FCD frame which has been received correctly must always be set to\ \*Q0\*U. 
.PP
The frame construction of PPR response is shown in
Figure\ A\(hy3/T.30.
.PP
The process of an error correction is shown in
Figure\ A\(hy4/T.30.
.PP
\fINote\ 1\fR \ \(em\ The number of frames in a partial page is less than or
equal to 256\ frames. Therefore, in some circumstances there may be extra 
bits that do not correspond to any frames. These bits are set to \*Q1\*U 
(see 
Figure\ A\(hy5/T.30).
.PP
\fINote\ 2\fR \ \(em\ The first bit in the FIF corresponds to the first frame
(frame No.\ 0).
.RT
.LP
	2)
	\fIReceive not ready (RNR)\fR \ \(em\ This signal is used to
indicate that the receiver is not ready to receive more data.
.LP
	Format:\ X011\ 0111
.LP
	\fINote\ 1\fR \ \(em\ This signal is defined for flow control.
.LP
	\fINote\ 2\fR \ \(em\ For flow control, make reference to \(sc\ A.5.
.LP
	3)
	 \fIResponse for end of retransmission (ERR)\fR \ \(em\ This signal is 
the digital response to EOR signal. 
.LP
	Format:\ X011\ 1000
.bp
.LP
.rs
.sp 13P
.ad r
\fBFigure A\(hy3/T.30, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 29P
.ad r
\fBFigure A\(hy4/T.30, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 28P
.ad r
\fBFigure A\(hy5/T.30, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
A.5
	\fIFlow control procedure\fR 
.sp 1P
.RT
.PP
A.5.1
Flow control in the transmitting station is made by continuous flag transmission 
between frames or before the first frame. 
.sp 9p
.RT
.PP
A.5.2
The maximum transmission time of flags should be less than the
value of timer\ T1.
.PP
A.5.3
In case of transmission on a noisy channel, a long flag
sequence may be destroyed by noise. Therefore, it is recommended that the
receiver implement a control procedure to discard invalid frames which are
obtained from erroneous flag sequences.
.PP
A.5.4
Flow control in the receiving station is made using RR/RNR
signals as shown in Figure\ A\(hy6/T.30.
.LP
A.5.4.1\ \ Inactivity timer T5 is defined as follows:
.LP
	T5 = 60 s \(+- 5 s.
.PP
\fINote\fR \ \(em\ As the use of the T5 timer reduces transmission
efficiency, implementation which minimizes its effect is desirable.
.LP
A.5.4.2\ \ The timer T5 is started at the timing of the first RNR response
recognition.
.LP
A.5.4.3\ \ If the timer T5 has expired, the transmitter sends a DCN command
for call release.
.LP
A.5.4.4\ \ If RNR response is not received correctly, an RR command is
retransmitted to the receiver. After three unsuccessful attempts, the
transmitter sends a DCN command for call release.
.LP
A.5.4.5\ \ After receiving RNR response, the transmitter immediately
sends an RR command until an MCF/PIP response or an ERR/PIN response is
received correctly.
.LP
A.5.4.6\ \ An MCF or ERR response indicates that the busy condition is cleared
and the receiver ready to receive the data which follows the
interruption.
.bp
.LP
.rs
.sp 35P
.ad r
\fBFigure A\(hy6/T.30, (N), p.6\fR 
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
A.6
	\fIProcedure interrupt\fR 
.sp 1P
.RT
.PP
A.6.1 
Procedure interrupt signals are not allowed at the partial page
boundaries.
.sp 9p
.RT
.PP
A.6.2 
Procedure interrupt after detection or transmission of PIP
and\ PIN signals is accomplished by using the procedure defined in the 
main body of this Recommendation. This procedure is outside the scope of 
the error 
correction mode specified in this Annex\ A.
.sp 9p
.RT
.sp 2P
.LP
A.7
	\fIFlow Diagrams\fR 
.sp 1P
.RT
.PP
The following flow diagrams shows the phase B, pre\(hymessage
procedures, phase\ C, message procedure, phase\ D, post\(hymessage procedures 
and 
phase\ E, call release, for both the transmitting and receiving stations.
.PP
For the Notes and an explanation of terms to the flow diagrams, see
\(sc\ A.7.1.
.bp
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy7/T.30 (feuillet 1 sur 2), (N), p.7\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy7/T.30 (feuillet 1 sur 2), (N), p.8\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy7/T.30 (feuillet 2 sur 2), (N), p.9\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy7/T.30 (feuillet 2 sur 2), (N), p.10\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy8/T.30, (N), p.11\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy9/T.30, (N), p.12\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy10/T.30, (N), p.13\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy11/T.30, (N), p.14\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy12/T.30, (N), p.15\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy13/T.30, (N), p.16\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy14/T.30, (N), p.17\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy15/T.30, (N), p.18\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy16/T.30, (N), p.19\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy17/T.30, (N), p.20\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy18/T.30, (N), p.21\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy19/T.30, (N), p.22\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy20/T.30, (N), p.23\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy21/T.30, (N), p.24\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy22/T.30, (MC), p.25\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy23/T.30, (MC), p.26\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy24/T.30, (N), p.27\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy25/T.30, (N), p.28\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
A.7.1
	\fIFlow diagram key\fR 
.sp 1P
.RT
.LP
COMMAND\ REC
The \*Qcommand received\*U subroutine searches for an error\(hyfree
standard command. The decision diamonds in the flow diagram
refer to the most recent standard command received (e.g.,\ EOM,
MPS,\ etc.).
COMPT\ REMOTE
REC
The FIF associated with the DIS has indicated a \*Qcompatible remote
receiver\*U.
DOC\ TO\ XMIT
The station has \*Qat least one document to be transmitted\*U.
.LP
COMPT\ REMOTE
XMTR
The FIF associated with the DIS has indicated a \*Qcompatible
remote transmitter\*U which has documents to send.
RESPONSE\ REC
The \*Qresponse received\*U subroutine which searches for an error\(hyfree
standard response.
LAST\ DOC
The \*Qlast document\*U, for the given operating mode, has been
transmitted.
SET\ MODE
The system controller will \*Qset the appropriate mode\*U of
operation.
.LP
3RD\ TRY
The command has been repeated three times without an appropriate
response.
CAPABLE\ RE\(hyXMIT
The transmitting station is \*Qcapable of retransmitting\*U a document
which was not received with acceptable quality.
MSG\ CARRIER
REC
The \*Qmessage channel carrier has been received\*U. This carrier is
1800\ Hz for the Group\ 3 modulation scheme, and 1700\ Hz for the
Group\ 3 optional modulation scheme, 2100\ Hz for the Group\ 2 modulations,
and 1300\(hy2100\ Hz for the Group\ 1 modulation scheme.
.LP
PHASE/TRAIN\ OK
The phasing/training\(hyTCF signal has been analyzed and the results of
\*Qphasing/training were OK\*U.
CHANGE\ MODE
The transmitting unit desires to exit from the transmitting mode of
operation and reestablish the capabilities.
NSP\ REQ
A \*Qnon\(hyspecified procedure\*U has been \*Qrecognized\*U by a unit 
compatible with the station initiating that procedure. 
COPY\ QUALITY\ OK
By some algorithm, the \*Qcopy quality was deemed OK\*U.
.LP
REPHASE/TRAIN
By some algorithm, it is deemed desirable to transmit a new
phasing/training signal.
FLAG
There has been the detection of a \*Qflag\*U.
RECEIVE\ A\ FRAME
The unit has \*Qreceived one complete HDLC frame\*U.
FCS\ ERROR
The HDLC frame received contained an \*QFCS error\*U.
.LP
OPTIONAL\ RESPNS
The HDLC frame received contained one of the listed \*Qoptional
responses\*U.
OPTIONAL
COMMAND
The HDLC frame received contained one of the listed \*Qoptional
commands\*U.
CRP\ OPTION
The facsimile unit has the \*QCRP option\*U and can, therefore,
request an immediate retransmission of the most recent command.
.LP
LOCAL\ INT
Either the \*Qlocal\*U machine or the \*Qlocal\*U operator wishes to generate
an interrupt of the standard facsimile procedures. An operator
would use this as a means to request the establishment of voice
contact.
LINE\ REQ
This means that the local operator has \*Qrequested\*U that the telephone
line be connected to the handset for voice contact with the remote
end.
PRI\(hyQ
A general term referring to either PRI\(hyEOM, a PRI\(hyMPS, or a PRI\(hyEOP
post\(hymessage command, i.e.,\ the fifth bit of the standard post\(hymessage
command is set to\ 1.
END\ OF\ PAGE?
The transmitting station may have further data to transmit to complete
the page.
.LP
4TH\ PPR?
PPR has been received 4 times.
TRANSMIT\ ERROR
FRAMES
The frames defined in the information field associated with PPR are
transmitted using the V.27 | fIter\fR /V.29 modulation system.
CONTINUE\ TO
CORRECT?
The transmitting station by some algorithm decides to continue
correcting the previous message.
.bp
.LP
CONT\ WITH
NEXT\ MSG?
The transmitting station by some algorithm decides to continue
and transmit the next message. The previous message was not satisfactorily
transmitted.
.LP
PPS\(muPRI\(hyQ?
The terminal has \*Qreceived either PPS\(muPRI\(hyEOM, PPS\(muPRI\(hyMPS, or
PPS\(muPRI\(hyEOP post\(hymessage command\*U.
PPS\(muQ?
The terminal has \*Qreceived either PPS\(muEOM, PPS\(muMPS, PPS\(muEOP
or PPS\(muNull post\(hymessage command.\*U
EOR\(muPRI\(hyQ?
The terminal has \*Qreceived either EOR\(muPRI\(hyEOM, EOR\(muPRI\(hyMPS, or
EOR\(muPRI\(hyEOP post\(hymessage command.\*U
EOR\(muQ?
The terminal has \*Qreceived either EOR\(muEOM, EOR\(muMPS, EOR\(muEOP or
EOR\(muNull post\(hymessage command\*U.
.LP
RECEIVE\ READY?
The receiving station is ready to receive the next message.
RR\ RESPONSE
REC?
The \*QRR response received\*U subroutine searches for an error\(hyfree
response for the RR command.
CTC\ RESPONSE
REC?
The \*QCTC response received\*U subroutine searches for an error\(hyfree
response for the CTC command.
.PP
\fINote\ 1\fR \ \(em\ The non\(hyspecified procedure, NSP, refers to a 
procedure which takes 6\ seconds or less to complete. It may not necessarily 
be a 
definable signal sequence.
.PP
\fINote\ 2\fR \ \(em\ This signal pertains to Group 3 apparatus only.
.PP
\fINote\ 3\fR \ \(em\ The PRI\(hyEOM, PRI\(hyEOP, PRI\(hyMPS post\(hymessage 
commands are sent when a local interrupt request is pending. 
.PP
\fINote\ 4\fR \ \(em\ At any time during the operation an interrupt may 
be generated which would result in a procedural interrupt. It is understood 
that if this 
interrupt happens during the transmission of the document, the EOM/RTC
signal will be transmitted prior to invoking the procedural interrupt.
.PP
\fINote\ 5\fR \ \(em\ Where the symbol / is used, the term to the left of the
symbol refers to Groups\ 1 and\ 2 equipment, and the term to the right of the
symbol refers to Group\ 3 equipment.
.PP
\fINote\ 6\fR \ \(em\ Where the symbols {  } are used, the signals within these
symbols are a response to DIS from the calling unit wishing to receive.
.PP
\fINote\ 7\fR \ \(em\ Where the symbols (\ ) are used, the signals within these
symbols are optional.
.RT
.sp 1P
.LP
A.8
	\fISignal sequence examples in case of\fR \fIerror correction procedure\fR 
.sp 9p
.RT
.PP
The examples below are based on the flow diagrams and for
illustrative and instructional purposes only. They should not be interpreted 
as establishing or limiting the protocol. The exchange of the various commands 
and responses is limited only by the rules specified in this Recommendation. 
.PP
In these diagrams the dashed lines indicate transmission at the
message data rate (Recommendation\ V.27 | fIter\fR , V.29), and (X, Y) 
means (page 
modulo number, block modulo number).
.RT
.LP
.rs
.sp 8P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 1 sur 13), (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 2 sur 13), (N), p.30\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 3 sur 13), (N), p.31\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 4 sur 13), (N), p.32\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 5 sur 13), (N), p.33\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 6 sur 13), (N), p.34\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 7 sur 13), (N), p.35\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 8 sur 13), (N), p.36\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 25P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 9 sur 13), (N), p.37\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 24P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 10 sur 13), (N), p.38\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 11 sur 13), (N), p.39\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 12 sur 13), (N), p.40\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure A\(hy26/T.30 (feuillet 13 sur 13), (N), p.41\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce 1000
APPENDIX\ I
.ce 0
.ce 1000
(to Recommendation T.30)
.sp 9p
.RT
.ce 0
.ce 1000
\fBExample of non\(hystandard manual\(hyto\(hymanual basic\fR \fBfacsimile 
operation\fR 
.sp 1P
.RT
.ce 0
.PP
It is acknowledged that there are existing equipments in the
field that may not conform in all aspects to this Recommendation. Therefore,
the decision may be made to go to a mode of operation other than specified
herein. Figure\ I\(hy1/T.30 describes, as an example, one of these conditions.
Other methods may be possible as long as they do not interfere with the
recommended operation.
.sp 1P
.RT
.LP
.rs
.sp 41P
.ad r
\fBFIGURE I\(hy1/T.30, (M), p.42\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce 1000
APPENDIX\ II
.ce 0
.ce 1000
(to Recommendation T.30)
.sp 9p
.RT
.ce 0
.LP
.sp 1
.ce
\fBH.T. [1T13.30]\fR 
.ce
\fBIndex of abbreviations used in Recommendation T.30\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(72p) | cw(72p) | cw(42p) .
Abbreviation 	Function 	Signal format 	Reference
_
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
CED	Called station identification	2100 Hz	4.3.3.2 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
CFR	Confirmation to receive	X010 0001	5.3.6.1.4, 1) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
		1850 or 1650 Hz  for 3s	4.3.1.2 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
CRP	Command repeat	X101 1000	5.3.6.1.8, 2) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
CIG	 {
Calling subscriber identification
 }	1000 0010	5.3.6.1.2, 2) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
CNG	Calling tone	1100 Hz for 500 ms	4.3.3.3
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
CSI	 {
Called subscriber identification
 }	0000 0010	5.3.6.1.1, 2) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
CTC	Continue to correct	X100 1000	A.4.1 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
CTR	 {
Response to continue to correct
 }	X010 0011	A.4.2 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
DCN	Disconnect	X101 1111	5.3.6.1.8, 1) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
DCS	Digital command signal	X100 0001	5.3.6.1.3, 1) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
DIS	Digital identification signal	0000 0001	5.3.6.1.1, 1)
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
DTC	Digital transmit command	1000 0001	5.3.6.1.2, 1) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
EOM	End of message	X111 0001 1100 Hz	5.3.6.1.6, 1)  4.3.2.4
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
EOP	End of procedure	X111 0100	5.3.6.1.6, 3)
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
EOR	End of retransmission	X111 0011	A.4.3 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
ERR	 {
Response for end of retransmission
 }	X011 1000	A.4.4 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
FCD	Facsimile coded date	0110 0000	A.2.2 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
FCF	Facsimile control field	\(em	5.3.6.1 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
FIF	Facsimile informtion field	\(em	5.3.6.2 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
FTT	Failure to train	X010 0010	5.3.6.1.4, 2)
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
GC	Group command	1300 Hz for 1.5\(hy10.0 s	4.3.2.1 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
		2100 Hz for 1.5\(hy10.0 s	
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
GI	Group identification	1650 or 1850 Hz	4.3.1.1 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
HDLC	High level data link control	\(em	5.3 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
LCS	Line conditioning signals	1100 Hz	4.3.2.2 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
MCF	Message confirmation	X011 0001  1650 or 1850 Hz	4.3.1.3 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
MPS	Multi\(hypage signal	X111 0010	5.3.6.1.6, 2) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
NSC	 {
Non\(hystandard facilities command
 }	1000 0100	5.3.6.1.2, 3) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
NSF	Non\(hystandard facilities	0000 0100	5.3.6.1.1, 3) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
NSS	Non\(hystandard set\(hyup	X100 0100	5.3.6.1.3, 3) 
_
.TE
.nr PS 9
.RT
.ad r
\fBTABLEAU II\(hy1/T.30 [1T13.30], p.43\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 7P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [2T13.30]\fR 
.ce
\fBIndex of abbreviations used in Recommendation T.30\fR 
.ce
\fI(end)\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(72p) | cw(72p) | cw(42p) .
Abbreviation 	Function 	Signal format 	Reference
_
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
PIN	Procedural interrupt negative	X011 0100	5.3.6.1.7, 5) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
PIP	Procedural interrupt positive	X011 0101	5.3.6.1.7, 4)
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
PIS	Procedure interrupt signal	462 Hz for 3 s	4.3.3.1 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
PPS	Partial page signal	X111 1101	A.4.3 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
PPR	Partial page request	X011 1101	A.4.4 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
PRI\(hyEOM	Procedure interrupt\(hyEOM	X111 1001	5.3.6.1.6, 4)
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
PRI\(hyEOP	Procedure interrupt\(hyEOP	X111 1100	5.3.6.1.6, 6)
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
PRI\(hyMPS	Procedure interrupt\(hyMPS	X111 1010	5.3.6.1.6, 5) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
RCP	 {
Return to control for partial page
 }	0110 0001	A.2.2 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
RNR	Receive not ready	X011 0111	A.4.4 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
RR	Receive ready	X111 0110	A.4.3 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
RTN	Retrain negative	X011 0010	5.3.6.1.7, 3)
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
RTP	Retrain positive	X011 0011	5.3.6.1.7, 2)
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
TCF	Training check	Zeros for 1.5 s	5.3.6.1.3, 4) 
.T&
cw(42p) | lw(72p) | cw(72p) | lw(42p) .
TSI	 {
Transmitting subscriber identification
 }	X100 0010	5.3.6.1.3, 2)
_
.TE
.nr PS 9
.RT
.ad r
\fBTABLEAU II\(hy1/T.30 [2T13.30], p.44\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 26P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.ce 1000
APPENDIX\ III
.ce 0
.ce 1000
(to Recommendation T.30)
.sp 9p
.RT
.ce 0
.ce
\fBH.T. [1T14.30]\fR 
.ce
\fBList of commands and appropriate responses\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(60p) | cw(108p) | cw(60p) .
Commands 	Comments 	Appropriate responses 
_
.T&
lw(60p) | lw(108p) | lw(60p) .
(NSF) (CSI) DIS	 {
Identifying capabilities:
from a manual receiver or an auto answer
unit.
 }	 {
(NSC) (CIG) DTC
(TSI) DCS
(NSF) (CSI) DIS
(CRP) (TSI) (NSS)
 }
_
.T&
lw(60p) | lw(108p) | lw(60p) .
(NSC) (CIG) DTC	 {
Mode setting command:
from the calling unit. 
This is
a poll operation.
 }	 {
(TSI) DCS 
(NSF) (CSI) DIS
(CRP) (TSI) (NSS)
 }
_
.T&
lw(60p) | lw(108p) | lw(60p) .
(TSI) DCS (TSI) (NSS)	 {
Mode setting command:
from manual transmitter or automatic
receiver. 
This command is always followed by phasing/training.
 }	 {
CFR 
FTT 
(NSC) (CIG) DTC
(NSF) (CSI) DIS
(CRP)
 }
_
.T&
lw(60p) | lw(108p) | lw(60p) .
CTC	 {
Mode setting command:
from the transmitter to the receiver.
 }	(CTR) (CRP)
_
.T&
lw(60p) | lw(108p) | lw(60p) .
(EOR\(muNULL)	 {
Indicate the next block transmission:
from the transmitter
to the receiver.
 }	(ERR)  (RNR) (CRP)
_
.T&
lw(60p) | lw(108p) | lw(60p) .
 {
(EOR\(muMPS) or
(EOR\(muEOP) or
(EOR\(muEOM) or
(EOR\(muPRI\(muMPS) or 
(EOR\(muPRI\(hyEOP) or 
(EOR\(muPRI\(hyEOM)
 }	 {
Indicate the next message transmission: 
from the transmitter to
the receiver.
 }	(ERR)  (RNR) PIN (CRP)
_
.T&
lw(60p) | lw(108p) | lw(60p) .
 {
MPS or EOP or EOM or
(PRI\(hyMPS) or 
(PRI\(hyEOP) or
(PRI\(hyEOM)
 }	Post message commands.	MCF  RTP RTN PIP  PIN (CRP)
_
.T&
lw(60p) | lw(108p) | lw(60p) .
(PPS\(muNULL)	 {
Post\(hymessage command for a partial page:
from the transmitter
to the receiver.
 }	(PPR)  MCF (RNR) (CRP)
_
.T&
lw(60p) | lw(108p) | lw(60p) .
 {
(PPS\(muMPS) or
(PPS\(muEOP) or 
(PPS\(muEOM) or 
(PPS\(muPRI\(hyMPS) or 
(PPS\(muPRI\(hyEOP) or
(PPS\(muPRI\(hyEOM)
 }	 {
Post\(hymessage commands for a complete page:
from the
transmitter to the receiver.
 }	 {
(PPR) 
MCF
(RNR)
PIP 
PIN
(CRP)
 }
_
.TE
.nr PS 9
.RT
.ad r
\fBTABLEAU III\(hy1/T.30 [1T14.30], p.45\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [2T14.30]\fR 
.ce
\fBList of commands and appropriate responses\fR 
.ce
\fI(end)\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(60p) | cw(108p) | cw(60p) .
Commands 	Comments 	Appropriate responses 
_
.T&
lw(60p) | lw(108p) | lw(60p) .
(RR)	 {
Ask for the status of the receiver:
from the transmitter to
the receiver.
 }	 {
(RNR) 
(ERR)
MCF
PIP 
PIN
(CRP)
 }
_
.T&
lw(60p) | lw(108p) | lw(60p) .
DCN	Phase E command	None 
.TE
.LP
\fINote\fR
\ \(em\ Where the symbols ( |  are used, the signals within these
symbols are optional.
.nr PS 9
.RT
.ad r
\fBTABLEAU III\(hy1/T.30 [2T14.30], p.46\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce 1000
APPENDIX\ IV
.ce 0
.ce 1000
(to Recommendation T.30)
.sp 9p
.RT
.ce 0
.ce 1000
\fBInterworking between the standard mode\fR 
.sp 1P
.RT
.ce 0
.ce 1000
\fBand the recognized optional mode for the binary coded\fR 
.ce 0
.ce 1000
\fBhandshaking procedure\fR 
.ce 0
.PP
An example of a station having the standard binary coded,
recognized optional binary coded and tonal capabilities is given in
Figure\ IV\(hy1/T.30.
.sp 1P
.RT
.LP
.rs
.sp 43P
.ad r
\fBFigure IV\(hy1/T.30, (MC), p.47\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce 1000
APPENDIX\ V
.ce 0
.ce 1000
(to Recommendation T.30)
.sp 9p
.RT
.ce 0
.ce 1000
\fBSignal sequence examples\fR 
.sp 1P
.RT
.ce 0
.PP
The examples below are based on the flow diagrams and are for illustrative 
and instructional purpose only. They should not be interpreted as establishing 
or limiting the protocol. The exchange of the various commands and responses 
is limited only by the rules specified in this Recommendation. 
(See \(sc\(sc\ 5.3 and\ 5.4).
.sp 1P
.RT
.PP
The notations used in these diagrams are as follows:
.LP
	\(em
	an arrowhead signifies the receiver of the signal;
.LP
	\(em
	 a solid line indicates transmission of the signal at the data rate of 
300\ bit/s; 
.LP
	\(em
	the dashed lines indicate transmission at the message data
rate (Recommendations\ V.27 | fIter\fR , V.29);
.LP
	\(em
	a lightning bolt (\ \ ) indicates an invalid frame;
.LP
	\(em
	a bold solid line indicates the transmission of tonal
signals.
.PP
In the following figures, the examples given assume that DIS will be repeated 
for T1\ seconds unless responded by a valid signal. 
.LP
.rs
.sp 33P
.ad r
\fBFigure V\(hy1/T.30, (MC), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure V\(hy2/T.30, (MC), p.49\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 34P
.ad r
\fBFigure V\(hy3/T.30, (MC), p.50\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 33P
.ad r
\fBFigure V\(hy4/T.30, (MC), p.51\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 23P
.ad r
\fBFigure V\(hy5/T.30, (MC), p.52\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 24P
.ad r
\fBFigure V\(hy6/T.30, (MC), p.53\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 29P
.ad r
\fBFigure V\(hy7/T.30, (MC), p.54\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 18P
.ad r
\fBFigure V\(hy8/T.30, (MC), p.55\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 11P
.ad r
\fBFigure V\(hy9/T.30, (MC), p.56\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 11P
.ad r
\fBFigure V\(hy10/T.30, (MC), p.57\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 10P
.ad r
\fBFigure V\(hy11/T.30, (MC), p.58\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 10P
.ad r
\fBFigure V\(hy12/T.30, (MC), p.59\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp