Toshiba DP120F, Service Manual

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March 2000 © TOSHIBA TEC 9-13 DP120F/DP125F Dialing and Communication Procedure
3. High-speed Transmission Procedure
The V.34 modem recommended by ITU-T (Max. transmission rate: 33.6 Kbps) is used. There-
fore, the transmission time of the image data is cut substantially when compared to conven-
tional model.
3.1 V.8/V.34 Procedure
a) Outline
• V.8 is performed as a start up procedure to switch to V.34. V.8 can connect an existing
facsimile machine to equipment using data modem or other V series modems. The V.34
modem includes a modem circuit which can also be connected to the previously recom-
mended modems. Therefore, it is downwardly compatible.
• The new techniques such as the pre-emphasis techniques *1 and the probing techniques
*2, are fully used. Pre-emphasis techniques not only make the speed of modulation method
high, but also gain the S/N ratio. Probing techniques measure the line characteristics and
optimize the modem for the line state. Therefore, these techniques do not simply speed-
ing-up transmission momentarily, but do so at the average level when the data transmis-
sion is actually performed.
• For V.8 and the pre/post-fax transmission for V.34, the procedure is speeded up by full
duplex communication.
• The following 14 types of image transmission speed are available: *3
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) can be selected from 2400, 3000, 3200 symbol/sec
(mandatory), or 2743, 2800, 3429 symbol/sec (option). The data rate can be set more
accurately than the conventional modem. *4
*1: A signal is sent by raising the output level in the high-frequency band - in which the
noise is relatively loud.
*2: The tone called “Probing Tone” is sent. The receiver measures the line characteris-
tics.
*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”. “Symbol rate”, “Modu-
lating speed”, and “Baud rate” have the same meaning. This machine cannot use the
speed of “2743 symbol/sec”.