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+
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+RFC 804
+
+
+ CCITT Draft Recommendation T.4
+
+
+ As Defined In: CCITT STUDY GROUP XIV, CONTRIBUTION No.25-E
+
+SOURCE: DRAFTING GROUP ON DRAFT RECOMMENDATION T.4
+TITLE: DRAFT RECOMMENDATION T.4 - STANDARDIZATION OF GROUP 3
+ FACSIMILE APPARATUS FOR DOCUMENT TRANSMISSION (as
+ amended and agreed by Working Party XIV/2)
+
+Draft Recommendation T.4
+
+STANDARDIZATION OF GROUP 3 FACSIMILE APPARATUS FOR DOCUMENT
+TRANSMISSION
+
+The CCITT, considering
+
+a. that Recommendation T.2 refers to Group 1 type apparatus
+ for ISO A4 document transmission over a telephone-type
+ circuit in approximately six minutes;
+b. that Recommendation T.3 refers to Group 2 type apparatus
+ for ISO A4 document transmission over a telephone-type
+ circuit in approximately three minutes:
+c. that there is a demand for Group 3 apparatus which
+ enables an ISO A4 document to be transmitted over a
+ telephone-type circuit in approximately one minute;
+d. that for a large number of applications black and white
+ reproduction is sufficient;
+e. that such a service may be requested either
+ alternatively with telephone conversation, or when
+ either or both stations are not attended; in both cases,
+ the facsimile operation will follow Recommendation T.30,
+
+(unanimously) declares the view that Group 3 facsimile
+apparatus for use on the general switched telephone network
+and international leased circuits should be designed and
+operated according to the following standards:
+
+
+1. Scanning track
+
+ The message area should be scanned in the same
+direction in the transmitter and receiver. Viewing the
+message area in a vertical plane, the scanning direction
+should be from left to right and subsequent scans should be
+adjacent and below the previous scan.
+
+
+2. Dimensions of apparatus
+
+CCITT Draft Recommendation T.4 PAGE 2
+
+
+
+ The following dimensions should be used:
+
+a. A normal definition standard and an optional higher
+ definition standard of 3.85 and 7.7 line/mm respectively
+ in vertical direction;
+b. 1728 black and white picture elements along the scanned
+ line;
+c. A scanning line length of 215 mm. Other scanning line
+ lengths may be employed in which case the scanning
+ density should be changed to maintain the correct
+ picture proportions;
+d. Input documents up to a minimum of ISO A4 size should be
+ accepted.
+
+3. Transmission time per scanning line
+
+ A total scanning line is defined as the sum of DATA
+bits plus any required FILL bits plus the EOL bits. The
+minimum transmission times of the total scanning line should
+conform to the following:
+
+a. 20 milliseconds recommended standard with an optional
+ fall-back to the 40 milliseconds option;
+b. 10 milliseconds recognized option with a mandatory
+ fall-back to the 20 milliseconds standard;
+c. 5 milliseconds recognized option with a mandatory
+ fall-back to the 10 milliseconds option and the 20
+ milliseconds standard;
+d. 40 milliseconds recognized option.
+
+ The identification and choice of this minimum
+transmission time is to be made in the pre-message (Phase B)
+portion of the T.30 control procedure. The maximum
+transmission time of any total scanning line should be less
+than 5 seconds.
+
+4. Coding scheme
+
+ The one-dimensional run length encoding scheme
+recommended for Group 3 apparatus is as follows:
+
+a. DATA
+ A line of data is composed of a series of variable
+ length code words. Each code word represents a run
+ length of either all white or all black. White runs and
+ black runs alternate. A total of 1728 picture elements
+ represent one horizontal scanning line of the document
+ of standard A4 size. In order to insure that the
+ receiver maintains color synchronization, all DATA lines
+ will begin with a white run length code word. If the
+ actual scanning line begins with a black run, a white
+ run length of zero will be sent. Black or white run
+ lengths, up to a maximum length of one scanning line
+
+CCITT Draft Recommendation T.4 PAGE 3
+
+
+
+ (1728 picture elements or pels) are defined by the code
+ words in Tables 1 and 2. The code words are of two
+ types: Terminating Code words and Make Up Code words.
+ Each run length is represented by either one Terminating
+ Code word or one Make Up Code word followed by a
+ Terminating Code word.
+
+ Run lengths in the range of 0 to 63 pels are encoded
+ with their appropriate Terminating Code word. Note that
+ there is a different list of code words for black and
+ white run lengths.
+
+ Run lengths in the range of 64 to 1728 pels are encoded
+ first by the Make Up Code word representing the run
+ length which is equal to or shorter than that required.
+ This is then followed by the Terminating Code word
+ representing the difference between the required run
+ length and the run length represented by the Make Up
+ Code.
+
+b. END OF LINE (EOL)
+
+ This code word follows each line of DATA. It is a
+ unique code word that can never be found within a valid
+ line of DATA; therefore, resynchronization after an
+ error burst is possible.
+
+ In addition, this signal will occur prior to the first
+ DATA line of a page.
+
+ Format: 000000000001
+
+c. FILL
+
+ A pause may be placed in the message flow by
+ transmitting FILL. FILL may be inserted between a line
+ of DATA and an EOL, but never within a line of DATA.
+ Fill must be added to insure that each line of DATA,
+ FILL, and EOL exceeds the minimum transmission time of a
+ total scanning line established in the premessage
+ control procedure. The maximum length for a single line
+ of FILL is 5 seconds, after which the receiver may
+ disconnect.
+
+ Format: variable length string of 0's.
+
+d. RETURN TO CONTROL (RTC)
+
+ The end of a document transmission is indicated by
+ sending six consecutive EOL's. Following the RTC
+ signal, the transmitter will send the post message
+ commands in the standard T.30 blocked format at the data
+ rate.
+
+CCITT Draft Recommendation T.4 PAGE 4
+
+
+
+ Format: 000000000001 ... ... ... ... 000000000001
+ (total of 6 times)
+
+CCITT Draft Recommendation T.4 PAGE 5
+
+
+
+ Table 1a. Terminating White Codes
+ Code Lng Run
+ ---------------------------
+ 00110101 8 0
+ 000111 6 1
+ 0111 4 2
+ 1000 4 3
+ 1011 4 4
+ 1100 4 5
+ 1110 4 6
+ 1111 4 7
+ 10011 5 8
+ 10100 5 9
+ 00111 5 10
+ 01000 5 11
+ 001000 6 12
+ 000011 6 13
+ 110100 6 14
+ 110101 6 15
+ 101010 6 16
+ 101011 6 17
+ 0100111 7 18
+ 0001100 7 19
+ 0001000 7 20
+ 0010111 7 21
+ 0000011 7 22
+ 0000100 7 23
+ 0101000 7 24
+ 0101011 7 25
+ 0010011 7 26
+ 0100100 7 27
+ 0011000 7 28
+ 00000010 8 29
+ 00000011 8 30
+ 00011010 8 31
+ 00011011 8 32
+ 00010010 8 33
+ 00010011 8 34
+ 00010100 8 35
+ 00010101 8 36
+ 00010110 8 37
+ 00010111 8 38
+ 00101000 8 39
+ 00101001 8 40
+ 00101010 8 41
+ 00101011 8 42
+ 00101100 8 43
+ 00101101 8 44
+ 00000100 8 45
+ 00000101 8 46
+ 00001010 8 47
+ 00001011 8 48
+ 01010010 8 49
+
+CCITT Draft Recommendation T.4 PAGE 6
+
+
+
+ 01010011 8 50
+ 01010100 8 51
+ 01010101 8 52
+ 00100100 8 53
+ 00100101 8 54
+ 01011000 8 55
+ 01011001 8 56
+ 01011010 8 57
+ 01011011 8 58
+ 01001010 8 59
+ 01001011 8 60
+ 00110010 8 61
+ 00110011 8 62
+ 00110100 8 63
+
+CCITT Draft Recommendation T.4 PAGE 7
+
+
+
+ Table 1b. Make Up White Codes
+ Code Lng Run
+ ---------------------------
+ 11011 5 64
+ 10010 5 128
+ 010111 6 192
+ 0110111 7 256
+ 00110110 8 320
+ 00110111 8 384
+ 01100100 8 448
+ 01100101 8 512
+ 01101000 8 576
+ 01100111 8 640
+ 011001100 9 704
+ 011001101 9 768
+ 011010010 9 832
+ 011010011 9 896
+ 011010100 9 960
+ 011010101 9 1024
+ 011010110 9 1088
+ 011010111 9 1152
+ 011011000 9 1216
+ 011011001 9 1280
+ 011011010 9 1344
+ 011011011 9 1408
+ 010011000 9 1472
+ 010011001 9 1536
+ 010011010 9 1600
+ 011000 6 1664
+ 010011011 9 1728
+
+CCITT Draft Recommendation T.4 PAGE 8
+
+
+
+ Table 2a. Terminating Black Codes
+ Code Lng Run
+ ---------------------------
+ 0000110111 10 0
+ 010 3 1
+ 11 2 2
+ 10 2 3
+ 011 3 4
+ 0011 4 5
+ 0010 4 6
+ 00011 5 7
+ 000101 6 8
+ 000100 6 9
+ 0000100 7 10
+ 0000101 7 11
+ 0000111 7 12
+ 00000100 8 13
+ 00000111 8 14
+ 000011000 9 15
+ 0000010111 10 16
+ 0000011000 10 17
+ 0000001000 10 18
+ 00001100111 11 19
+ 00001101000 11 20
+ 00001101100 11 21
+ 00000110111 11 22
+ 00000101000 11 23
+ 00000010111 11 24
+ 00000011000 11 25
+ 000011001010 12 26
+ 000011001011 12 27
+ 000011001100 12 28
+ 000011001101 12 29
+ 000001101000 12 30
+ 000001101001 12 31
+ 000001101010 12 32
+ 000001101011 12 33
+ 000011010010 12 34
+ 000011010011 12 35
+ 000011010100 12 36
+ 000011010101 12 37
+ 000011010110 12 38
+ 000011010111 12 39
+ 000001101100 12 40
+ 000001101101 12 41
+ 000011011010 12 42
+ 000011011011 12 43
+ 000001010100 12 44
+ 000001010101 12 45
+ 000001010110 12 46
+ 000001010111 12 47
+ 000001100100 12 48
+ 000001100101 12 49
+
+CCITT Draft Recommendation T.4 PAGE 9
+
+
+
+ 000001010010 12 50
+ 000001010011 12 51
+ 000000100100 12 52
+ 000000110111 12 53
+ 000000111000 12 54
+ 000000100111 12 55
+ 000000101000 12 56
+ 000001011000 12 57
+ 000001011001 12 58
+ 000000101011 12 59
+ 000000101100 12 60
+ 000001011010 12 61
+ 000001100110 12 62
+ 000001100111 12 63
+
+CCITT Draft Recommendation T.4 PAGE 10
+
+
+
+ Table 2b. Make Up Black Codes
+ Code Lng Run
+ ---------------------------
+ 0000001111 10 64
+ 000011001000 12 128
+ 000011001001 12 192
+ 000001011011 12 256
+ 000000110011 12 320
+ 000000110100 12 384
+ 000000110101 12 448
+ 0000001101100 13 512
+ 0000001101101 13 576
+ 0000001001010 13 640
+ 0000001001011 13 704
+ 0000001001100 13 768
+ 0000001001101 13 832
+ 0000001110010 13 896
+ 0000001110011 13 960
+ 0000001110100 13 1024
+ 0000001110101 13 1088
+ 0000001110110 13 1152
+ 0000001110111 13 1216
+ 0000001010010 13 1280
+ 0000001010011 13 1344
+ 0000001010100 13 1408
+ 0000001010101 13 1472
+ 0000001011010 13 1536
+ 0000001011011 13 1600
+ 0000001100100 13 1664
+ 0000001100101 13 1728
+
+CCITT Draft Recommendation T.4 PAGE 11
+
+
+
+Note: It is recognized that machines exist which accommodate
+larger paper widths whilst maintaining the standard
+horizontal resolution. This option has been provided for by
+the addition of the Make Up Code Set defined as follows:
+
+
+
+ Table 3. Extended Make Up Codes (Black and White)
+ Code Lng Run
+ ---------------------------
+ 00000001000 11 1792
+ 00000001100 11 1856
+ 00000001101 11 1920
+ 000000010010 12 1984
+ 000000010011 12 2048
+ 000000010100 12 2112
+ 000000010101 12 2176
+ 000000010110 12 2240
+ 000000010111 12 2304
+ 000000011100 12 2368
+ 000000011101 12 2432
+ 000000011110 12 2496
+ 000000011111 12 2560
+
+ The identification and choice of either the standard
+code table or the extended code table is to be made in the
+pre-message (Phase B) portion of the T.30 control
+procedures.
+
+4.2 Two dimensional coding scheme
+
+ The one-dimensional coding scheme defined in 4.1 may be
+extended as an option to a two-dimensional scheme. This is
+the subject of further study.
+
+5. Modulation and demodulation method
+
+ It is provisionally agreed that Group 3 apparatus
+operating on the general switched telephone network shall
+utilize the modulation scrambler, equalization and timing
+signals defined in Recommendation V.27ter, specifically in
+the preamble and 2, 3, 6, 7, 9 and 10.
+
+ The data signalling rates to be used are those
+recommended in Recommendation V.27ter, i.e. 4800 and 2400
+bit/s.
+
+Note 1: Some administrations pointed out that it would not
+be possible to guarantee the service at a data signalling
+rate higher than 2400 bit/s.
+
+Note 2: It should be noted that there are equipments in
+service using, inter alia, other modulation methods. The
+
+CCITT Draft Recommendation T.4 PAGE 12
+
+
+
+arrangement of interworking between equipment conforming to
+Recommendation T.4 and these existing equipments is subject
+to further study.
+
+Note 3: For higher speed operation, such as may be possible
+on leased circuits, it is provisionally agreed that Group 3
+apparatus may utilize the signals specifically defined in 1,
+2, 3, 4, 7, 8, 9, 11, and 12 of Recommendation V.29.
+ \ No newline at end of file