User manual

CHAPTER 4: GENERAL INFORMATION AND FEATURES
4.10 Auto Dial Back-Up
When you apply the modem to leased lines, no matter what protocol you are using, in
case that the lines don't function well, you may allow modem dial a stored number via
a dial line to rebuild the connection. This line is called "back-up line."
While using the back-up line, the modem periodically checks the recovery of leased
lines to find the opportunity to go back to leased lines in order to save the charge of
dial line.
To use this function, you must set "leased To Dial" and "Dial To Leased" to be
"AUTO" or "MANUAL" under "LINE SETUP" menu; also fill up "Backup Tel#1"
and recovery time.
4.11 Auto Fallback And Fall Forward
When auto fallback & fall forward is enabled in V.34 or V.32bis mode, the modem
will automatically initial a V.34 or V.32bis rate renegotiation when the line condition
changes, so that the optimum available data rate is always select with minimal
interruption to user data.
To use this function, the "FF/FB control " under "CONFIG MODEM"menu must set
to be on.
4.12 Line Status Monitoring
In order to let users manage transmission conditions, the Network Series
Modem provides a signal quality displayed at right lower corner of the screen. It
ranges from 0 to 9. The following shows the relationship between the displayed
number and bit error rate (BER).
9 -- < 10 ^ -9
8 -- < 10 ^ -8
7 -- < 10 ^ -7
6 -- < 10 ^ -6
5 -- < 10 ^ -5
4 -- < 10 ^ -4
3 -- < 10 ^ -3
2 -- < 10 ^ -2
1 -- < 10 ^ -1
0 -- NO Connect
Basically, 10^-5 to 10^-6 is the basic required bit error rate. If this condition is not
achievable; leased line users should report to telephone company, however, it is better
for dial line users to try the dial again.
There are some real time line condition information which may help you judge the
line quality:
Examples :
1. Transmitted signal level Tx level = -10 dBm
2. Received signal level Rx level = -25 dBm
3. Signal to noise ratio S/N Ratio = 35 dB
4. Received frequency shift F-Shift = 0.2 Hz
5. Far-end frequency shift F F-Shift = 1.7 Hz
6. Round trip delay Delay = 560 ms
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