US Robotics 56K USB Modem User Manual page 45

Table 70. Valid <direction> Values
Value*
0 Does not negotiate V.42bis compression.
3 Modem accepts V.42bis compression in both direction (default).
* ITU-T Recommendation V.250 (05/99) standardized this command. The standard command includes two additional parameter val-
ues (1 and 2), which are not supported by the controller-based AT command set. For additional information on the functionality of
the <direction parameter, refer to ITU-T Recommendation V.250 (05/99).
The <compression_negotiation> parameter tells the modem whether it should disconnect if V.42
negotiations fail. The controller-based AT command set does not support the disconnect feature when V.42
negotiation fails, and the <compression_negotiation> parameter is always set to 0. The default dictionary,
<max_dict> size, is always 1024, and the default string length, <max_string>, is always 32.
Table 71. +DS Extended Syntax Commands
Command
+DS=<direction>,0,1024,32
+DS?
+DS=?
+DS44=<direction>,<compression_negotiation>,<capabil-
ity>,<max_codewords_tx>, <max_codewords_rx>,
<max_string_tx>,<max_string_rx>,<max_history_tx>,<max_history_rx>—V.44
Data Compression
Use this command to configure the V.44 data compression method used by the modem. This controller-
based modem only supports the stream method for capability and does not support the disconnect feature
if V.44 is not negotiated (for compression negotiation). As a result, both parameters,
<compression_negotiation> and <capability>, are always 0.
Result codes:
• OK if <direction> = 0, 3 and <compression_negotiation> = 0 and <compatibility> = 0 and
<max_codewords_tx> = 256—2048 and <max_codewords_rx> = 256—2048 and <max_string_tx> =
31—255 and <max_string_rx> = 31—255 and <max_history_tx> = 512—11008 and <max_history_rx>
= 512—11008.
ERROR if <direction> ≠ 0, 3 or <compression_negotiation> ≠ 0 or <compatibility> ≠ 0 or
•
<max_codewords_tx> ≠ 256—2048 or <max_codewords_rx> ≠ 256—2048 or <max_string_tx> ≠ 31—
255 or <max_string_rx> ≠ 31—255 or <max_history_tx> ≠ 512—11008 or <max_history_rx> ≠ 512—
11008.
The <direction> parameter sets which directions use the compression method. USRobotics controller-
based products use compression in one or both directions.
Table 72. Valid <direction> Values
Value
0 Do not negotiate V.44 compression.
3 Modem accepts V.44 compression in both direction (default).
The <max_codewords_tx> parameter specifies the maximum number of code words to negotiate in the
transmit direction. The <max_codewords_rx> parameter specifies the maximum number of code words to
negotiate in the receive direction.
Meaning
Description
Configures modem V.42 compression method.
Displays the current V.42 compression configuration.
Displays the supported V.42 compression setting.
Meaning
56K USB Modem
User Guide
Command Reference - 39