From 4bfd864f10b68b71482b35c818559068ef8d5797 Mon Sep 17 00:00:00 2001 From: Thomas Voss Date: Wed, 27 Nov 2024 20:54:24 +0100 Subject: doc: Add RFC documents --- doc/rfc/rfc804.txt | 475 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 475 insertions(+) create mode 100644 doc/rfc/rfc804.txt (limited to 'doc/rfc/rfc804.txt') diff --git a/doc/rfc/rfc804.txt b/doc/rfc/rfc804.txt new file mode 100644 index 0000000..a0320eb --- /dev/null +++ b/doc/rfc/rfc804.txt @@ -0,0 +1,475 @@ + + + + +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 -- cgit v1.2.3