Fuji Xerox DocuCentre SC2020 Service Manual page 699

V.8 procedure uses CNG (or CI: for Manual Send) sent by the outgoing terminal and ANSam tonal
(sound) signal sent by the incoming terminal. If the line is noisy or the signal level is low, these tonal sig-
nals cannot be recognized properly by the remote station and resulting in errors. Procure the protocol of
the remote station and determine whether the signals (recorded in one's Trace) sent from here are
recorded.
V.34 procedure is being carried out in order of Phase 2, 3, and 4, and [V34ph2], [V34ph3], and [V34ph4]
is recorded in the Protocol Trace. If Phase 4 has completed successfully, proceed to Phase B, C, D, and
E. Please refer to the procedure in the past for the troubleshooting here.
When the line is noisy or the signal is low, the procedure is not carried out properly. When Phase 2, 3,
and 4 is being carried out repeatedly, [V34ph2], [V34ph3], [V34ph4], [V34ph2], [V34ph3], [V34ph4]... will
be recorded in the Protocol Trace repeatedly. If error occurred in the procedure of Phase 2, [V34ph2] is
recorded but not [V34ph3] and [V34ph4].
It can determine whether there is a problem with the analog characteristics of the telephone line in both
examples described here and determine if the Send level is not appropriate.
Send level: As Super G3 Fax is analog communication, the signal level is very important. Especially
when the noise level ratio (known as S/N ratio) becomes an issue. To detect the signal correctly, the S/N
ratio must be above a certain level. Verify the Protocol Trace, if the remote station indicates 'Same signal
is sent repeatedly', 'Do not advance to the next procedure', or the likes, it will mean that the remote sta-
tion cannot recognize the signal from here.
In such cases, you can try changing the Send Level. If the Send Level is increased with the same noise
level, S/N ratio becomes larger. When changing the Send Level, slowly increase or decrease the level (1-
2dB) and test the communication several times with the changed value to find the best value.
However, if digital lines (ISDN/Corporate Digital Leased Line) or digital devices (such as digital PBX/TA)
are used, analog signal with too high a level will cause the wave pattern to become erratic and the com-
munication cannot take place normally (when performing analog-digital modulation, the wave pattern of
high level signals is erratic). In line environment like this, lower the Send Level for satisfactory communi-
cation.
Speed: The highest speed is 33600bit/s for Super G3 mode; however, most of the PSTN communica-
tions in Japan are performed in 31200~21600 bit/s. If the line condition is very bad, the speed may be
reduced to 9600bit/s. Communication speed is determined by the result of Phase 2 procedure for V.34
Send Terminal. Therefore, even if the same line is used, a change in the Send Terminal will affect the
communication speed.
Version 1.1
DC SC2020
Line Frequency Characteristics (F attribute): Attributes for telephone line frequency is known as [Fre-
quency Characteristic], and ideally, the characteristic is uniform between 300 to 3400Hz used by the tele-
phone. However, for public lines, it is normal for the lower frequency and the higher frequency to
deteriorate (attenuation distortion, delayed signals), and the deterioration extent increases as the ground
distance (accurately speaking, the line distance for the analog section) becomes longer. As compared to
normal telephone calls and G3 Fax communication, the Frequency Characteristics for Super G3 commu-
nication is greatly affected. Even for lines that can carry out 14000/9600bps communication normally,
error may occur in Super G3 communication. As audio compression is being performed in most of the
Corporate Leased Lines (digital lines), the Frequency Characteristic is worst than the NTT public line,
resulting in a high level of error occurrences in Super G3 communication.
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6.6.5.5 Troubleshooting of Super G3 Fax
General