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5 Binary coded signalling for facsimile procedure
For Group 1 and Group 2 machines that require additional facilities to
those provided by the procedures described in S 4 above, the binary coded control
procedures should be transmitted in a synchronous mode at 300 bits per second.
For Group 3 machines, 300 bits per second is the standard data signalling
rate for the transmission of binary coded procedural data. Additionally,
signalling of the binary coded procedural data at 2400 bits per second is allowed
as a recognized option.
For Group 3 machines, an error correction capability is utilized as a
recognized option. This procedure is defined in Annex A.
Except as otherwise noted, the binary coded control procedures should be
transmitted in a synchronous mode on the general switched telephone network at
300 bits per second ± 0.01% utilizing the characteristics of the
Recommendation V.21 channel No. 2 modulation system. (For the tolerances, see S 3
of Recommendation V.21.) Signal generators should have a distortion not
exceeding 1% and the control signal receivers should accept signals with a
distortion not exceeding 40%.
Note 1 - For Group 3 machines, the transmission of training, TCF, and all
in-message signals, shall be at the data rate of the high-speed message channel.
Note 2 - It is acknowledged that existing equipments may not conform in
all aspects to this Recommendation. Other methods may be possible as long as they
do not interfere with the recommended operation.
Note 3 - Transmission of signals utilizing the modulation system of
Recommendation V.21 channel No. 2 should be followed by a delay of
75 ± 20 milliseconds before the signalling, utilizing a different modulation
system commences (e.g. the delay between DCS and the Recommendation V.27 ter,
V.29, V.33 or V.17 training sequence).
Note 4 - The transmission of signalling utilizing the modulation systems
of Recommendations V.27 ter, V.29, V.33 or V.17 should be followed by a delay of
75 ± 20 milliseconds before the signalling, utilizing a different modulation
system, commences (e.g. the delay between RTC and MPS).
Note 5 - Group 3 machines using the modulation system defined in V.17 (as
specified by bits 11, 12, 13 and 14 of Table 2/T.30) shall use the short
resynchronization sequence defined in Table 3/V.17 for all trellis mode training
except during a TCF message and the first high speed message after a CTC/CTR ECM
message sequence. The long synchronization sequence shall be used in the TCF and
the first high speed message after the CTC/CTR sequence.
include 30-T01-E
A.7.1 Flow diagram key
COMMAND REC The "command received" subroutine searches for an error-free
standard command. The decision diamonds in the flow diagram
refer to the most recent standard command received (e.g., EOM,
MPS, etc.).
COMPT REMOTE The FIF associated with the DIS has indicated a "compatible
remote receiver".
REC
DOC TO XMIT The station has "at least one document to be transmitted".
COMPT REMOTE The FIF associated with the DIS has indicated a "compatible
remote transmitter" which has
XMTR documents to send.
RESPONSE REC The "response received" subroutine which searches for an error-
free standard response.
LAST DOC The "last document", for the given operating mode, has been
transmitted.
SET MODE The system controller will "set the appropriate mode" of
operation.
3RD TRY The command has been repeated three times without an appropriate
response.
CAPABLE RE-XMIT The transmitting station is "capable of retransmitting" a
document which was not received with acceptable quality.
MSG CARRIER The "message channel carrier has been received". This carrier is
1800 Hz for the Group 3
REC modulation scheme, and 1700 Hz for the Group 3 optional
modulation scheme, 2100 Hz for the Group 2 modulations,
Fascicle VII.3 - Recommendation T.30PAGE
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and 1300-2100 Hz for the Group 1 modulation scheme.
PHASE/TRAIN OK The phasing/train-TCF signal has been analyzed and the results
of "phasing/training were OK".
CHANGE MODE The transmitting unit desires to exit from the transmitting mode
of operation and reestablish the capabilities.
NSP REQ A "non-specified procedure" has been "recognized" by a unit
compatible with the station initiating that procedure.
COPY QUALITY OK By some algorithm, the "copy quality was deemed OK".
REPHASE/TRAIN By some algorithm, it is deemed desirable to transmit a new
phasing/train signal.
FLAG There has been the detection of a "flag".
RECEIVE A FRAME The unit has "received one complete HDLC frame".
FCS ERROR The HDLC frame received contained an "FCS error".
OPTIONAL RESPNS The HDLC frame received contained one of the listed "optional
response".
OPTIONAL The HDLC frame received contained one of the listed "optional
commands".
COMMAND
CRP OPTION The facsimile unit has the "CRP option" and can, therefore,
request an immediate retransmission of the most recent command.
LOCAL INT Either the "local" machine or the "local" 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 "requested" that the
telephone line be connected to the handset for voice contact
with the remote end.
PRI-Q A general term referring to either PRI-EOM, a PRI-MPS, or a PRI-
EOP post-message command, i.e., the fifth bit of the standard
post-message command is set to 1.
END OF PAGE? The transmitting station may have further data to transmit to
complete the page.
4TH PPR? PPR has been received 4 times.
TRANSMIT ERROR The frame defined in the information field associated with PPR
are transmitted using the FRAMES V.27 ter/V.29/V.33/V.17
modulation system.
CONTINUE TO The transmitting station by some algorithm decides to continue
correcting the previous CORRECT? message.
CONT WITH The transmitting station by some algorithm decides to continue
and transmit the next message. NEXT MSG? The previous message was
not satisfactorily transmitted.
PPS · PRI-Q? The terminal has "received either PPS · PRI-EOM, PPS · PRI-MPS
or PPS · PRI-EOP post-message command".
PPS · Q? The terminal has "received either PPS · EOM, PPS · MPS, PPS ·
EOP or PPS · Null post-message command".
EOR · PRI-Q? The terminal has "received either EOR · PRI-EOM, EOR ·PRI-MPS,
or EOR · PRI-EOP post-message command".
EOR · Q? The terminal has "received either EOR · EOM, EOR · MPS, EOR ·
EOP or EOR · Null post-message command".
RECEIVE READY? The receiving station is ready to receive the next message.
RR RESPONSE The "RR response received" subroutine searches for an error-free
response for the RR
REC? command.
CTC RESPONSE The "CTC response received" subroutine searches f r an error-
free response for the CTC REC? command.
Note 1 - The non-specified procedure, NSP, refers to a procedure which
takes 6 seconds or less to complete. It may not necessarily be a definable signal
sequence.
Note 2 - This signal pertains to Group 3 apparatus only.
Note 3 - The PRI-EOM, PRI-EOP, PRI-MPS post-message commands are sent when
a local interrupt request is pending.
Note 4 - 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.
PAGE4 Fascicle VII.3 - Recommendation T.30
Note 5 - 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.
Note 6 - Where the symbols {} are used, the signals within these symbols
are a response to DIS from the calling unit wishing to receive.
Note 7 - Where the symbols ( ) are used, the signals within these symbols
are optional.
A.8 Signal sequence examples in case of error correction procedure
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.
The notations used in these diagrams are as follows:
- the dashed lines indicate transmission at the message data rate
(Recommendations V.27 ter, V.29, V.33, V.17 and (X, Y) means (page
modulo number, block modulo number).
APPENDIX V
(to Recommendation T.30)
Signal sequence examples
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 SS 5.3 and 5.4.)
The notations used in these diagrams are as follows:
- an arrowhead signifies the receiver of the signal;
- a solid line indicates transmission of the signal at the data rate of
300 bit/s;
- the dashed lines indicate transmission at the message data rate
(Recommendations V.27 ter, V.29, V.33, V.17;
- a lighting bolt ( ) indicates an invalid frame;
- a bold solid line indicates the transmission of tonal signals.
In the following figures, the examples given assume that DIS will be
repeated for T1 seconds unless responded by a valid signal.
FIGURE V-1/T.30
Fascicle VII.3 - Recommendation T.30PAGE
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