Motorola 326X V.34 - Manual (Page 136)

A-14 Configuration Quick Reference
Configur
ation
Q
uick-Ref
e
re
nce
AT * AP1 =On The modem monitors telephone line signal quality and negotiates the highest possible rate for a
modem’s modulation mode. You must enable Retrain (AT
* RT) to use the Adaptive Rate.
Close rear panel switch 1 down so that the modem can inform the terminal of rate changes See
“Configuring the Modem’s Dual In-line Package (DIP) Switches” section in this appendix for
information.
Adaptive Rate Operation in V.34 Modulation Mode
In the V.34 modulation mode, with Adaptive Rate=On (MODULATION OPTS Menu, or
AT
*
AP1), the modem selects the optimum data rate on the first connection. The modem then
monitors line conditions, and if conditions deteriorate (i.e., poor signal quality), the modems
retrain and determine the rate that the line can support, within the range specified in Max Rate
(AT
*
MX) and Min Rate (AT
*
MN). Under poor line conditions, the modem may fall back by
more than one rate.
For example, at a data rate of 28.8 kbps, under poor line conditions, the modem may retrain to
19.2 kbps instead of 21.6 kbps. ARS adjustment is based on the High/Low BER setting of the
AT
*
RT (Retrain) option.
NOTES:
1) The AT
*
RT (Retrain) command must be enabled (set to Low BER or High BER)
if you use the adaptive rate setting.
2) The modem does not fall forward in V.34 modulation mode with ARS enabled.
Line Probing Feature Operation in V.34 Mode
The modem uses a line probing feature during the initial training sequence. Line probing
selects the maximum data rate that the line can support, as well as the optimal baud rate and
carrier frequency. Due to this, in the V.34 modulation modes (V.34 Auto and V.34 Only), the
modem may require a longer training sequence.
NOTE: For a summary of the supported data rates, baud rates and carrier frequencies, refer to
the “V.34 Modulation Mode Characteristics” section in Chapter 1.
If You Operate the Modem in V.34 Mode with ARS Disabled...
If you operate the modem in the V.34 modulation mode with the ARS option disabled
(AT
*
AP0), the modem selects the optimum data rate that can be supported (as determined by
the line probing feature described above) on the first connection.
With ARS disabled, the modem does not automatically fall back when line conditions
deteriorate.
NOTE: When external timing is selected, configure the modem so that the minimum rate is
equal to the maximum rate. This will force the modems to come up at a specific data rate only.
Asym Rate V.34 Asymmetric Rate
Controls whether the modem permits different transmit and receive DCE rates.
AT * AR0 =Off Asymmetric Rate
AT * AR1 =On
Ans Rest Answer In Restoral
Controls whether the modem answers a call on the dial line while connected to the leased line.
AT * AS0 =LL Fail When connected on a leased line, the modem answers an incoming call only if the leased line
fails.
Table A-1.
AT Commands, Cross-Referenced to Front Panel Options (Continued)
AT
Command Parameter &
Option
Description
Gray shading indicates country-specific options. See Appendix C for your country’s options.