Black Box MD885C-R2 Modem User Manual


 
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4.0 General Operation and Special Features
If Rate Renegotiation Procedure (RRP) is enabled, the modem will
automatically fall back or fall forward to a lower or higher data rate in
response to changes in signal quality. This may happen at any time during
data transmission, and it is done without a retraining procedure. Your data
transmission is virtually uninterrupted.
Note that data-rate adjustments are limited:
to the range of 4800 to 14,400 bps for the Modem
(4800 to 9600 bps for the Modem 3242–S)
by the minimum and maximum rate settings of the Speed Limit option.
If satisfactory performance cannot be attained at any of the available data
rates, the Modem will initiate a GSTN cleardown (line disconnect). If the
originate modem attempts to negotiate a rate that is lower than the minimum
rate setting of the answer modem, the answer modem will initiate a GSTN
cleardown.
How to Enable or Disable RRP
NOTE
RRP will function only if Speed Fallback is enabled (factory default) and
if the V.32 Mode option is set to V.32 bis (factory default). Both functions
are Summary Setup options.
The factory-default setting for RRP is enabled. To change the RRP option,
refer to the DATA PUMP OPTIONS diagram in Appemdix C. Change the
Rate Renegotiation Procedure (RRP) parameter shown in the diagram to 0
(disable) or 1 (enable). This is the only way the RRP option can be changed.
Rate Change Screen
If V.32 bis mode and the Rate Renegotiation Procedure (RRP) option are
both enabled, the Modem will automatically adjust during data transmission
to a higher or lower data rate, depending on the receive signal quality. For
diagnostic purposes, the RATE screen (accessed from screen 3 of the MAIN
MENU, as illustrated below) may be used to manually initiate speed renego-
tiation from the front panel, as explained below.
NOTE
The RATE screen is only displayed if V.32 bis mode is enabled
(via Summary Setup, V.32 Mode option).
If you select DOWN from the RATE screen, the Modem will fall back to the
next-lower speed. If you select UP, the modem will fall forward to the next-
higher speed if the signal quality is good enough. Remember, the data-speed
range within which the Modem can fall forward or fall back is limited by the
minimum and maximum rates set via the Speed Limit option.