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3.2.3
V.8/V.34 communication sequence
1. Outline
-
V.8 is performed as a startup procedure to switch to V.34. V.8 can connect an existing facsimile
machine to the equipment using a data modem or other V-series modems. The V.34 modem has
a modem circuit previously recommended, allowing it to be also connected to the existing
modems while they are upper compatible.
-
New technologies such as the pre-emphasis technology (*1) and the probing technology (*2) are
fully used. The pre-emphasis technology (*1) not only speeds up the modulation, but also gains
the S/N ratio. The probing technology examines the line characteristics and optimizes the
modem for the line conditions. Therefore, not only do these technologies speed up the
transmission momentarily, but also the overall speed of the process during the data transmission
is increased.
-
For V.8 and the pre/post-fax transmission for V.34, the procedure is speeded up by the full duplex
communication.
-
Following 14 types of the image transmission speed (*3) are available.
33.6 kbps / 31.2 kbps / 28.8 kbps / 26.4 kbps / 24.0 kbps / 21.6 kbps / 19.2 kbps / 16.8 kbps / 14.4
kbps / 12.0 kbps / 9.6 kbps / 7.2 kbps / 4.8 kbps / 2.4 kbps
-
The modulating speed (baud rate) (*4) can be selected from 2,400, 3,000, 3,200 symbol/sec
(mandatory), or 2,800, 3,429 symbol/sec (option). The data rate can be set more accurately than
the conventional modem.
*1 A signal is sent while raising the output level in the high-frequency band in which the noise is
relatively loud.
*2 Tone signal called "Probing Tone" is sent for the receiver to examine the line characteristics of
the line.
*3 In the ITU-T Recommendation, it is described as "data rate". "Image transmission speed" is
the same as "data rate".
*4 In the ITU-T Recommendation, it is described as "symbol speed". The "Symbol rate",
"Modulating speed", and "Baud rate" are the same thing.
Remarks:
•
ECM is used in the V.34 procedure. If the setting for the ECM transmission/reception of the
user data is set to "Not performed", the V.8 procedure is not performed and the procedure is
not switched to V.34. V.17 or lower is selected in this case.
•
See P. 3-20 "- Late start" to move to the V. 8/V.34 procedure after starting with the V.21
procedure.
•
After the V.34 procedure is started, the fallback for the V.34 procedure is performed.
However, the fallback for the V.17 mode or lower mode is not performed.
GD-1370
DIALING/COMMUNICATION CONTROL
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