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         The text approved is: 
         Fascicle VII.3 - Rec. T.4 
         4.3    Extended two-dimensional coding scheme 
               The basic facsimile coding scheme specified in S 2.2 of Recommendation  T.6 
         may be used as an option in Group 3 facsimile. This coding scheme is  limited  to 
         the use of the Error Correction Mode specified in S 3.3. 
         4.4    Error limiting mode 
               One-dimensional coding scheme with the division of scan line into parts. 
               The one-dimensional coding scheme with  the  division  of  scan  line  into 
         parts is an optional extension of the one-dimensional coding scheme specified  in 
         Annex B. 
         5      Modulation and demodulation 
               Group 3 apparatus operating  on  the  general  switched  telephone  network 
         shall utilize the modulation, scambler, equalization and timing  signals  defined 
         in Recommendation V.27 ter, specifically SS 2, 3, 7, 8, 9, 11 and the Appendix. 
         5.1    The training signal to be used shall be the long  training  sequence  with 
         protection against talker echo (see  Recommendation  V.27  ter,  S  2.5.1,  Table 
         3/V.27 ter). 
         5.2    The data signalling rates to be used are 4800  bit/s  and  2400  bit/s  as 
         defined in Recommendation V.27 ter. 
               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. 
               Note 3 — Where quality of communication service  can  successfully  support 
         higher speed operation, such as may  e  possible  on  leased  circuits  or  high- 
         quality  switched  circuits.  Group  3  apparatus  may  optionally  utilize   the 
         modulation, scrambler, equalization and timing signals defined in Recommendations 
         V.29, V.33 and V.17. For V.29 this specifically refers to SS 1, 2, 3, 4, 7, 8, 9, 
         10 and 11. Under this option the data should be non-multiplexed  and  limited  to 
         the  data  signalling  rates  of  9600  bit/s  and  7200  bit/s.  For  V.33  this 
         specifically refers to SS 1, 2, 3, 4, 7 and 8. Under this option the data  should 
         be non-multiplexed. For V.17 this specifically refers to SS 1 through 5. 
               Note  4 — When V.33  signalling  is  used  the  training  signal  shall  be 
         preceded by a Talker Echo Protection signal. The Talker  Echo  Protection  signal 
         shall consist of an unmodulated carrier for a  duration  of  185  ms  to  200  ms 
         followed by a silent period of 20 to 25 ms. 
               Note 5 — When V.17 signalling is used the  training  signal  shall  include 
         the Talker Echo Protection (TEP) signal defined in S 5.3/V.17. 
         6      Power at the transmitter output 
               The average power should be adjustable from  —15  dBm  to  0  dBm  but  the 
         equipment should be so designed that there is no possibility of  this  adjustment 
         being tampered with by an operator. 
               Note — The power levels over the international  circuits  will  conform  to 
         Recommendation V.2. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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