Leased Line Dial-Backup - ZyXEL Communications U-1496 series User Manual

The U-1496, U-1496R, U-1496P, and U-1496E support both asynchronous and synchronous
leased line operation. Choose a suitable modem link mode. If the signal to noise ratio of your
leased line is guaranteed above 25 dB, V.32bis 14400 is a better choice. V.32bis 14400 is also
compatible with V.32bis 12000/7200 and V.32 9600T/9600/4800. You can use ZyX 16800 or ZyX
19200 mode if the S/N ratio is better than 27 or 28dB.

LEASED LINE DIAL-BACKUP

When a leased line connection fails, some actions may be taken by the U-1496 or U-1496R.
1. Retry to connect on the leased line indefinitely if dial back-up option is disabled.
2. If dial backup is enabled, the originating modem attempts to dial a pre-stored telephone
number to backup the connection; the answering modem will retry to connect on the leased line
and monitor the dial-up line for rings. Only U-1496 and U-1496R have the dial backup function
and capability. They have separate dial-up and leased line phone jacks/connectors.
DIAL BACKUP
The dial backup option can be set by issuing an asynchronous AT command from the terminal,
or by using the front panel control.
+ DISABLED
PH0-PH8
originate mode modem will automatically dial the number stored in the memory address
selected. The answer mode modem will monitor the dial-up line for rings.
The originating modem will try to dial the number up to nine times or until a 3-minute timer
timeout happens. If the dial backup attempt fails, the originating modem will go back to try the
leased line connection. If this fails, it will try the dial-up line again.
It will try these two alternatives indefinitely. If the dial backup attempt succeeds, the value of S-
Register S34 determines the interval of dial backup connection before going back to check the
leased line.
S34=0; Keep using dial backup line indefinitely.
S34=n; Retry leased line after `n' minutes (n=1-25, default is 30). If the leased line has
still not recovered, the modem will continue to use the dial backup line.
A semi-auto dial backup is selected if S44.2=1. In this mode, when making dial backup, the
modem will display "DIAL BACKUP?" and wait for the user's confirmation. Only when the panel
confirmation is pressed will the modem start the dial backup. This saves unnecessary dial
backup connection when the line is not in use, e.g., non-business hours.
ABORT FROM LEASED LINE
If the leased line has not been connected, pressing any key on the front panel will abort the
attempt to connect on the leased line. If dial backup is enabled, backup action will be taken.
Pressing any key again will abort the backup action, and revert to IDLE SCREEN.
AT*B0 Leased line dial backup disabled (Default).
AT*B1-9 When leased line cannot continue operation. The