V.34 Modulation - Paradyne COMSPHERE 3920Plus Technical Reference Manual

When the Digital Bridging feature is enabled, a new menu is present with the following conditions:
• TDM capability is disabled when DTE Bridge configuration option is set to Enable,
• Configuration options are provided for Port 1 only; Port 2 cannot be configured.
• Ports 3 and 4 are not available.
• Port-related tests, such as digital loopbacks and Pattern tests, are available for Port 1.
• DTE Status, Health and Status, and LED control are available for both Ports 1 and 2.

V.34 Modulation

The V.34 modulation capability is available in all 392xPlus modems. In Singleport mode the V.34
modulation is compatible with other vendors' modems that support the ITU-T V.34 modulation. In
Multiport mode, the V.34 modulation will not operate at line rates of 31,200, 26,400, and 21,600
bps.
The ITU-T standard for V.34 modulation includes dial- or leased-line operation. For proper
leased-line operation, one modem must be designated as the answer modem while the other
modem must be designated as the originate modem.
The V.34 standard also includes asymmetric rates, automatic adjustment of the transmit power
level, and automatic adjustment of the symbol (baud) rate for optimal data throughput. These
automatic adjustments are made during the training, or modem synchronization, phase via special
line-probing techniques that establish the top-most viable rate of operation. Due to these
techniques, true fixed-rate operation of the modems using V.34 modulation is not possible, since
the line condition may not be capable of supporting the selected rate. Thus, using CT111 and
CT112 for rate control of extended data circuits cannot be used.
When operating in V.34 modulation, you can use the top line of the Quick Configuration screen to
view the current modem transmit rate, the symbol or baud rate, and the transmit level. The
392xPlus modems offer separate options for leased and dial lines to override the asymmetric rate
function, since this can cause problems for certain DTE equipment, Also, each symbol rate
supports a subset of data rates, which make up the whole of the V.34 standard.
When using the V.34 modulation on leased lines with a 2-wire leased backup facility, the backup
line check feature, which tests the backup leased lines for connectivity, cannot be used.
3920-A2-GH30-40
therefore the rate of Port 1 is forced to run at the line rate.
Symbol Rate
3429
3200
3000
2800
2743
2400
October 1998
Supported Data Rates
4800 – 33.6K
4800 – 31.2K
4800 – 28.8K
4800 – 31.2K
4800 – 31.2K
2400 – 24.0K
Introduction
1-9