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(Please note that this is the basic AT Command set.  Many modems do NOT conform to this command set.  However, most of these commands remain the same, or similar from modem to modem.  This section includes 4 important s-registers for dealing with dropped connections, however please keep in mind that these registers can vary from modem to modem.)

Quickly Referenced Commands

*Hn  -  "Link Negotiation(MNP10)"

"Hn  -  "v.42bis Compression Options"

"Nn  -  "v.42bis Data Size"

"On  -  "v.42bis Max String Length"

-Jn  -  "v.42bis Detect Control"

-Kn  -  "Extended MNP Control"

-Qn  -  "MNP10 Fallback Control"

)Mn  -  "Power Level Adjustment"

@Mn  -  "Transmission Level"

:En  -  "v.32 Compromise Equalizer Control"

+MS=n  -  "Modulation"

s10=n  -  "Loss of Carrier Response"

s25=n  -  "DTR Ignore Time"

s30=n  -  "Inactivity Timer"

s91=n  -  "Transmission Level"

Verbosely Referenced Commands

*Hn  -  "Link Negotiation(MNP10)"  -  This command selects the link negotiation speed for MNP10.

   *H0  -  Highest speed possible

   *H1  -  1200bps

   *H2  -  4800bps

"Hn  -  "v.42bis Compression Options"  -  This command selects different modes for v.42bis.

   "H0  -  Disabled

   "H1  -  When transmitting v.42bis is enabled

   "H2  -  When receiving v.42bis is enabled

   "H3  -  v.42bis is enabled both when transmitting and receiving

"Nn  -  "v.42bis Data Size"  -  Selects the block size of the v.42bis data

   "N0  -  512 bytes

   "N1  -  1024 bytes

   "N2  -  1536 bytes

"On  -  "v.42bis Max String Length"  -  This Command selects the string length of the v.42bis compression option.  The range is from 6-64 characters.

-Jn  -  "v.42bis Detect Control"  -  This command enables or disables v.42bis detection.

   -J0  -  Disabled

   -J1  -  Enabled

-Kn  -  "Extended MNP Control"  -  This command selects whether extended MNP services are used or not.

   -K0  -  Disabled

   -K1  -  Enabled

   -K2  -  Enabled except during answer mode

-Qn  -  "MNP10 Fallback Control"  -  This command allows or disallows MNP10 to fallback to 2400bps or 1200bps.

   -Q0  -  Disabled

   -Q1  -  Enabled

)Mn  -  "Power Level Adjustment"  -  This command controls the power level adjustment when transmitting during the MNP10 link negotiation.

   )M0  -  Disabled

   )M1  -  Enabled

@Mn  -  "Transmission Level"  -  This command controls the signal level for the transmission.

    @M0  -  -26dBm

   @M1  -  -30dBm

   @M2  -  -10dBm

:En  -  "v.32 Compromise Equalizer Control"  -  This command enables or disables the v.32 compromise equalizer.

    :E0  -  Disabled

   :E1  -  Enabled

+MS=n  -  "Modulation"  -  This command can select the active protocol, automode selection, min and max rates, min and max tx rates, min and max rx rates, and/or the x law.  This command varies from modem to modem and is seldom used for non-56k modems.  It would be best to consult the modem chipset for proper modulation control.

s10=n  -  "Loss of Carrier Response"  -  This command tells the modem how long to wait until hanging up after losing the carrier signal.  The setting ranges from 1-255 and is measured in .1 second intervals.

s25=n  -  "DTR Ignore Time"  -  This command sets the max amount of time that a change in the DTR signal will be ignored before the modem hangs up.  The setting ranges from 0-255 and is measured in .1 second intervals.

s30=n  -  "Inactivity Timer"  -  This command sets the max amount of time that the modem will wait for DTE and DCE to become active before hanging up.  The setting ranges from 0-255 and is measured in 10 second intervals.

s91=n  -  "Transmission Level"  -  This command sets the signal level for a transmission.  The setting ranges from 1-15 and is measured in units of -1dBm.