Paradyne 392xPLUS operation manual Multiport Backup, Symbol Rate Supported Data Rates

COMSPHERE 392xPlus Modems

The CCITT 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.

Symbol Rate	Supported Data Rates
3429	4800 ± 33.6K
	4800 ± 31.2K
3200
3000	4800 ± 28.8K
2800	4800 ± 31.2K
2743	4800 ± 31.2K
2400	2400 ± 24.0K

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.

NOTE

When a 2400 V.34 modulation connection occurs on one end of a modem pair with configuration options set for Asymmetric rates, the other modem is 24K due to the 2400 symbol rate it uses.

Multiport Backup

When the 392xPlus multiport modem has the MUX mode configuration option set to either TDM/MSD or Digital Bridge, it is in Multiport mode, and either dial lines or a 2-wire leased line can be used to back up the primary 4-wire leased line. Backup can be performed automatically upon loss of the primary leased line, and automatic dial standby also can be used to automatically return the modems to the primary leased line when restored.

When you use backup functions while in Multiport mode, the modem's automode feature is forced to Disable. This ensures that the mux is not accidentally disabled by answering a call, which is using modulation where Multiport mode is not supported. It is important that both modems participating in the backup are in Multiport mode with the same dial-line modulation.

1-10 November 1996 3920-A2-GN31-30