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010100 010001 111110 000111
110101 110000 111011 000010
011110 100111 001100 001001
011011 100010 101101 101000
-6
-4
180
000100 000001 001110 101111
111101 111000 001011 101010
010110 110111 100100 100001
010011 110010 011101 011000
Q
, Q
, Q
5n
4n
3n
Fig. 5-58 Signal Spatial Diagram at 12000 bps
Due to the relationship between transmission bandwidth and modulation
speed, the carrier frequency of V.29 is stipulated at 1700 Hz. When the car-
rier frequency of V.33 was studied by ITU-T, naturally, a MODEM for a
telephone line exclusive to V.29 of the same modulation speed and a
MODEM for a V.32 publicly switched telephone network were compared.
The carrier frequencies of each differed at 1700 Hz and 1800 Hz in spite of
the fact that they both used almost the same frequency bandwidth.
When the task of recommending the V.33 MODEM was rigorously delib-
erated by ITU-T, there was already broad consensus for the recommenda-
tion of the V.32 MODEM family, and the point of issue in the deliberation
became whether to select 1700 Hz, the carrier frequency of a V.29
MODEM, or to select the 1800 Hz of the V.32 MODEM family as the car-
rier frequency on a recommendation V.33 MODEM. As V.33 is positioned
as an extended version of the V.29 MODEM, there was a proposal from
various countries that the carrier frequency should be selected as 1700 Hz.
However, there was also a proposal that V.33 for recommending 1800 Hz,
G3 FACSIMILE COMMUNICATIONS
90
011100 011001 110110 010111
6
100101 100000 110011 010010
4
101110 001111 111100 111001
2
101011 001010 000101 000000
-2
2
101100 101001 100110 011111
-2
001101 001000 100011 011010
-4
000110 111111 110100 110001
-6
000011 111010 010101 010000
270
, Y
, Y
and Y
are indicated in binary.
2n
1n
0n
4
6
0
5–71
1
2
3
4
5
6
ït
çi
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