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<H1 ALIGN=CENTER><BR>
The Hayes Command Set </H1>

<P>
<HR SIZE=1></P>

<P><FONT SIZE=+1>Here is a description of the Hayes Command Set. Most modem
follow this command set to large extent. If you lost your modem manual
or never had one in the first place this reference might come in handy.
I for instance finally found out how to turn my modems speaker off: ATM0
-- Finally:&nbsp;Silence !</FONT></P>

<H2><A NAME="top"></A>The Hayes Command Set</H2>

<P>The modem initialization string consists of a series of commands. It
prepares the modem for communications, setting such features as dialing
mode, waits, detection of the busy signal and many other settings. Newer
modem communications programs reset the initializations string for you
according to which menu options you select, which features you enable,
etc.</P>

<P>For many years Hayes modems have been <B>the</B> standard. As the field
of modem manufactures has grown, most have adhered at least loosely to
the Hayes standard. The following is a partial list of the Hayes command
set. (called the AT commands). The <B>Hayes Command Set</B> can be divided
into four groups:</P>

<DL>
<DT>Basic Command Set </DT>

<DD>A capital character followed by a digit. For example, M1.</DD>

<DT>Extended Command Set </DT>

<DD>An &quot;&amp;&quot; (ampersand) and a capital character followed by
a digit. This is an extension of the basic command set. For example, &quot;&amp;M1&quot;.
Note that &quot;M1&quot; is different from &quot;&amp;M1&quot;.</DD>

<DT>Proprietary Command Set </DT>

<DD>Usually started by either a backslash (&quot;\&quot;), or a percent
sign (&quot;%&quot;), these commands vary widely among modem manufacturers.
For that reason, only a few of these commands are listed below.</DD>

<DT>Register Commands </DT>

<DD>Sr=n where &quot;r&quot; is the number of the register to be changed
and &quot;n&quot; is the new value that is being assigned. </DD>
</DL>

<P>A &quot;register&quot; is computerese for a specific physical location
in memory. Modem have small amounts of memory onboard. This fourth set
of commands is used to enter values in a particular register (memory location).
The register will be storing a particular &quot;variable&quot; (alpha-numeric
information) which is utilized by the modem and communication software.
For example, S7=60 instructs your computer to &quot;Set register #7 to
the value 60.&quot;</P>

<P><B>Note:</B> Although most commands are defined by a letter-number combination
(L0, L1, etc.), the use of a zero is optional. In this case, L0 is the
same as a plain &quot;L&quot; - keep this in mind when reading the table
below!</P>

<P>Here are some of the most important characters that may appear in the
modem initialization string. These characters normally should not be changed.</P>

<DL>
<DT><B>AT</B> </DT>

<DD>tells the modem that modem commands follow. This must begin each line
of commands.</DD>

<DT><B>Z</B> </DT>

<DD>resets the modem to default state</DD>

<DT><B>, (comma)</B> </DT>

<DD>makes your software pause for a second. You can use more than one ,
in a row. For example, &quot;,,,,&quot; tells the software to pause four
seconds. (The duration of the pause is governed by the setting of register
S8.</DD>

<DT><B>^M</B> </DT>

<DD>sends the terminating Carriage Return character to the modem. This
is a control code that most communication software translate as a &quot;carriage
return.&quot;</DD>
</DL>

<P>
<HR SIZE=1 NOSHADE></P>

<H2><A NAME="basicset"></A>The Basic Hayes Command Set - Alphabetical</H2>

<TABLE BORDER=1 WIDTH="100%" >
<TR>
<TH>Command </TH>

<TH>- Description - </TH>

<TH>Comments<BR>
</TH>
</TR>

<TR>
<TD><A NAME="A"></A>A0 or A </TD>

<TD>Answer incoming call<BR>
</TD>
</TR>

<TR>
<TD>A/ </TD>

<TD>Repeat last command. </TD>

<TD>(Don't preface with AT. Enter usually aborts.)<BR>
</TD>
</TR>

<TR>
<TD><A NAME="B"></A>B0 or B </TD>

<TD ROWSPAN=3>Call negotiation </TD>

<TD>V32 Mode/CCITT ans Seq <BR>
</TD>
</TR>

<TR>
<TD>B1 </TD>

<TD>Bell 212A Answer Seq <BR>
</TD>
</TR>

<TR>
<TD>B2 </TD>

<TD>Verbose/Quiet On Answer<BR>
</TD>
</TR>

<TR>
<TD><A NAME="D"></A>D </TD>

<TD>Dial </TD>

<TD>Dial the following number and then handshake in originate mode. 
<P>Dial Modifiers</P>

<P>(These are common but most modems will have more.)</P>

<DL COMPACT>
<DT>P </DT>

<DD>Pulse dial </DD>

<DT>T </DT>

<DD>Touch Tone dial </DD>

<DT>W </DT>

<DD>Wait for second dial tone </DD>

<DT>, </DT>

<DD>Pause for time specified in register S8 (usually 2 seconds) </DD>

<DT>; </DT>

<DD>Remain in command mode after dialing </DD>

<DT>! </DT>

<DD>Flash switch-hook (Hang up for a half second as in transferring a call)
</DD>

<DT>L </DT>

<DD>Dial last number </DD>
</DL>

<P><BR>
</P>
</TD>
</TR>

<TR>
<TD><A NAME="E"></A>E0 or E </TD>

<TD>No Echo </TD>

<TD>Will not echo commands to the computer<BR>
</TD>
</TR>

<TR>
<TD>E1 </TD>

<TD>Echo </TD>

<TD>Will echo commands to the computer (so one can see what one types)<BR>
</TD>
</TR>

<TR>
<TD><A NAME="H"></A>H0 or H </TD>

<TD ROWSPAN=2>Hook status </TD>

<TD>On hook - hang up<BR>
</TD>
</TR>

<TR>
<TD>H1 </TD>

<TD>Off hook - phone picked up<BR>
</TD>
</TR>

<TR>
<TD><A NAME="I"></A>I0 or I </TD>

<TD>Inquiry, Information, or Interrogation </TD>

<TD>(This command is very model specific. I0 usually returns a number or
code, while higher numbers often provide much more useful information.)<BR>
</TD>
</TR>

<TR>
<TD><A NAME="L"></A>L0 or L </TD>

<TD ROWSPAN=4>Speaker Loudness 
<P>Modems with volume control knobs will not have these options.<BR>
</P>
</TD>

<TD>Off or low volume<BR>
</TD>
</TR>

<TR>
<TD>L1 </TD>

<TD>Low volume <BR>
</TD>
</TR>

<TR>
<TD>L2 </TD>

<TD>Medium volume<BR>
</TD>
</TR>

<TR>
<TD>L3 </TD>

<TD>Loud or high volume <BR>
</TD>
</TR>

<TR>
<TD><A NAME="M"></A>M0 or M </TD>

<TD ROWSPAN="3">Speaker off </TD>

<TD>(M3 is also common, but different on many brands)<BR>
</TD>
</TR>

<TR>
<TD>M1 </TD>

<TD>Speaker on until remote carrier detected (until the other modem is
heard)<BR>
</TD>
</TR>

<TR>
<TD>M2 </TD>

<TD>Speaker is always on (data sounds are heard after CONNECT)<BR>
</TD>
</TR>

<TR>
<TD><A NAME="N"></A>N0 or N </TD>

<TD ROWSPAN=2>Handshake Speed </TD>

<TD>Handshake only at speed in <A HREF="#S37">S37</A><BR>
</TD>
</TR>

<TR>
<TD>N1 </TD>

<TD>Handshake at highest speed larger than <A HREF="#S37">S37</A><BR>
</TD>
</TR>

<TR>
<TD><A NAME="O"></A>O0 or O </TD>

<TD ROWSPAN=2>Return Online </TD>

<TD>(O0 see also X1 as dial tone detection may be active)<BR>
</TD>
</TR>

<TR>
<TD>O1 </TD>

<TD>Return Online after an equalizer retrain sequence<BR>
</TD>
</TR>

<TR>
<TD><A NAME="Q"></A>Q0 or Q </TD>

<TD ROWSPAN=2>Quiet mode </TD>

<TD>Off - Displays result codes, user sees command responses (e.g. OK)<BR>
</TD>
</TR>

<TR>
<TD>Q1 </TD>

<TD>On - Result codes are suppressed, user does not see responses<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S"></A>Sn? </TD>

<TD></TD>

<TD>Query the contents of S-register n<BR>
</TD>
</TR>

<TR>
<TD>Sn=r </TD>

<TD>Store </TD>

<TD>Store the value r in S-register n<BR>
</TD>
</TR>

<TR>
<TD><A NAME="V"></A>V0 or V </TD>

<TD ROWSPAN=2>Verbal? </TD>

<TD>Numeric result codes<BR>
</TD>
</TR>

<TR>
<TD>V1 </TD>

<TD>English result codes (e.g. CONNECT, BUSY, NO CARRIER etc.)<BR>
</TD>
</TR>

<TR>
<TD><A NAME="X"></A>X0 or X </TD>

<TD ROWSPAN=5>Smartmodem </TD>

<TD>Hayes Smartmodem 300 compatible result codes<BR>
</TD>
</TR>

<TR>
<TD>X1 </TD>

<TD>Usually adds connection speed to basic result codes (e.g. CONNECT 1200)<BR>
</TD>
</TR>

<TR>
<TD>X2 </TD>

<TD>Usually adds dial tone detection (preventing blind dial and sometimes
ATO)<BR>
</TD>
</TR>

<TR>
<TD>X3 </TD>

<TD>Usually adds busy signal detection<BR>
</TD>
</TR>

<TR>
<TD>X4 </TD>

<TD>Usually adds both busy signal and dial tone detection<BR>
</TD>
</TR>

<TR>
<TD><A NAME="Z"></A>Z0 or Z </TD>

<TD>Reset </TD>

<TD>Reset modem to stored configuration (Z0, Z1 etc. for multiple profiles)<BR>
(Same as &amp;F (factory default) on modems with out NVRAM (non volatile
memory)<BR>
</TD>
</TR>
</TABLE>

<P>
<HR SIZE=1 NOSHADE></P>

<H2><A NAME="extendedset"></A>The Extended Hayes Command Set<BR>
(Ampersand Commands )</H2>

<TABLE BORDER=1 WIDTH="100%" >
<TR>
<TH>Command </TH>

<TH>- Description - </TH>

<TH>Comments<BR>
</TH>
</TR>

<TR>
<TD><A NAME="ampB"></A>&amp;B0 or &amp;B </TD>

<TD ROWSPAN=3>Retrain Parameters </TD>

<TD>Disable auto retrain function<BR>
</TD>
</TR>

<TR>
<TD>&amp;B1 </TD>

<TD>Enable auto retrain function<BR>
</TD>
</TR>

<TR>
<TD>&amp;B2 </TD>

<TD>Enable auto retrain, but disconnect if no line improvement over period
dictated by <A HREF="#S7">S7</A><BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampC"></A>&amp;C0 or &amp;C </TD>

<TD ROWSPAN=2>Carrier detect </TD>

<TD>signal always on<BR>
</TD>
</TR>

<TR>
<TD>&amp;C1 </TD>

<TD>Indicates remote carrier (usual preferred default)<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampD"></A>&amp;D0 or &amp;D </TD>

<TD ROWSPAN=4>Data Terminal Ready (DTR) </TD>

<TD>Signal ignored (See your manual on this one!)<BR>
</TD>
</TR>

<TR>
<TD>&amp;D1 </TD>

<TD>If DTR goes from On to Off the modem goes into command mode (some modems)<BR>
</TD>
</TR>

<TR>
<TD>&amp;D2 </TD>

<TD>Some modems hang upon DTR On to Off transition. (Usual prefered default)<BR>
</TD>
</TR>

<TR>
<TD>&amp;D3 </TD>

<TD>Hang up, reset modem and return to command mode upon DTR<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampF"></A>&amp;F0 or &amp;F </TD>

<TD ROWSPAN=4>Factory defaults </TD>

<TD>Generic Hayes-compatible defaults. 
<P>This is usually a good thing to use in your init string, since the &amp;F1-&amp;F3
settings can vary among modems, and they may actually be the cause of connection
problems. (Since you never know exactly what Brand X's &amp;F2 <B>really</B>
changes.</P>

<P>On the other hand, it pays to try out the other options below; many
people's problems can be solved by replacing a complicated init string
with a simple &amp;F2 or the like. However, if you're building an init
string, it's best to start with a simple &amp;F, and not use the &quot;customized&quot;
form of defaults.<BR>
</P>
</TD>
</TR>

<TR>
<TD>&amp;F1 </TD>

<TD>Factory defaults tailored to an IBM-PC compatible user<BR>
</TD>
</TR>

<TR>
<TD>&amp;F2 </TD>

<TD>Factory defaults for a Mac w/software handshaking<BR>
</TD>
</TR>

<TR>
<TD>&amp;F3 </TD>

<TD>Factory defaults for a Mac w/hardware handshaking<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampG"></A>&amp;G0 or &amp;G </TD>

<TD>Guard tones </TD>

<TD>Disable guard tones<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampK"></A>&amp;K0 or &amp;K </TD>

<TD ROWSPAN=5>Local flow control </TD>

<TD>Disable local flow control<BR>
</TD>
</TR>

<TR>
<TD>&amp;K1 </TD>

<TD>Enable RTS/CTS hardware local flow control<BR>
</TD>
</TR>

<TR>
<TD>&amp;K2 </TD>

<TD>Enable XON/XOFF software local flow control<BR>
</TD>
</TR>

<TR>
<TD>&amp;K3 </TD>

<TD>Enable RTS/CTS hardware local flow control<BR>
</TD>
</TR>

<TR>
<TD>&amp;K4 </TD>

<TD>Enable XON/XOFF software local flow control<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampL"></A>&amp;L0 or &amp;L </TD>

<TD>Dial mode </TD>

<TD>Select dial-up mode<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampM"></A>&amp;M0 or &amp;M </TD>

<TD>Error Control mode </TD>

<TD>Select asynchronous non-EC mode (same as &amp;Q0)<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampP"></A>&amp;P0 or &amp;P </TD>

<TD ROWSPAN=2>Pulse dialing ratio </TD>

<TD>U.S./Canada pulse dialing 39% make/ 61% break ratio<BR>
</TD>
</TR>

<TR>
<TD>&amp;P1 </TD>

<TD>U.K./Hong Kong pulse dialing 33% make/ 67% break ratio<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampQ"></A>&amp;Q0 or &amp;Q </TD>

<TD ROWSPAN=5>Error Control mode </TD>

<TD>Asynchronous non-EC more. No data buffering. ASB disabled.<BR>
</TD>
</TR>

<TR>
<TD>&amp;Q5 </TD>

<TD>Select V.42 EC operation (requires flow control)<BR>
</TD>
</TR>

<TR>
<TD>&amp;Q6 </TD>

<TD>Asynchronous mode with ASB (requires flow control)<BR>
</TD>
</TR>

<TR>
<TD>&amp;Q8 </TD>

<TD>Select alternate EC protocol (MNP)<BR>
</TD>
</TR>

<TR>
<TD>&amp;Q9 </TD>

<TD>Conditional data compression: V.42bis = yes, MNP5 = no.<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampS"></A>&amp;S0 or &amp;S </TD>

<TD ROWSPAN=2>DSR Action Select </TD>

<TD>Always on (default)<BR>
</TD>
</TR>

<TR>
<TD>&amp;S1 </TD>

<TD>Follows EIA specification (Active following carrier tone, and until
carrier is lost.)<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampT"></A>&amp;T0 or &amp;T </TD>

<TD>Self test </TD>

<TD>Model specific self tests on some modems<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampU"></A>&amp;U0 or &amp;U </TD>

<TD ROWSPAN=2>Trellis code modulation </TD>

<TD>Enable V.32 TCM<BR>
</TD>
</TR>

<TR>
<TD>&amp;U1 </TD>

<TD>Disable V.32 TCM<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampV"></A>&amp;V0 or &amp;V </TD>

<TD>View active </TD>

<TD>(And often stored) configuration profile settings (or ATI4)<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampW"></A>&amp;W0 or &amp;W </TD>

<TD>Store profile </TD>

<TD>In NVRAM (&amp;W0, &amp;W1 etc. for multiple profiles)<BR>
Some settings cannot be stored. These often don't show on &amp;V or ATI4<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampY"></A>&amp;Y0 or &amp;Y </TD>

<TD ROWSPAN=2>Select Configuration Loaded at power-up </TD>

<TD>Load profile 0 (default)<BR>
</TD>
</TR>

<TR>
<TD>&amp;Y1 </TD>

<TD>Load profile 1<BR>
</TD>
</TR>

<TR>
<TD><A NAME="ampZ"></A>&amp;Zn=x </TD>

<TD>Soft reset and Load Stored profile #n </TD>

<TD>Note: All items after the &amp;Z on the command line are ignored<BR>
</TD>
</TR>
</TABLE>

<P>
<HR SIZE=1 NOSHADE></P>

<H2><A NAME="slash_pct"></A>Backslash &amp; Percent Commands:</H2>

<TABLE BORDER=1 WIDTH="100%" >
<TR>
<TH>Command </TH>

<TH>- Description - </TH>

<TH>Comments<BR>
</TH>
</TR>

<TR>
<TD><A NAME="bsA"></A>\A0 or \A </TD>

<TD ROWSPAN=4>Character maximum MNP block size </TD>

<TD>64 character maximum<BR>
</TD>
</TR>

<TR>
<TD>\A1 </TD>

<TD>128 character maximum<BR>
</TD>
</TR>

<TR>
<TD>\A2 </TD>

<TD>192 character maximum<BR>
</TD>
</TR>

<TR>
<TD>\A3 </TD>

<TD>256 character maximum<BR>
</TD>
</TR>

<TR>
<TD><A NAME="pctC"></A>%C0 or %C </TD>

<TD ROWSPAN=4>Data Compression Enable/Disable </TD>

<TD>Disabled<BR>
</TD>
</TR>

<TR>
<TD>%C1 </TD>

<TD>MNP5 Enabled<BR>
</TD>
</TR>

<TR>
<TD>%C2 </TD>

<TD>V.42bis (BTLZ) Enabled<BR>
</TD>
</TR>

<TR>
<TD>%C3 </TD>

<TD>MNP5 &amp; V.42bis (BTLZ) Enabled<BR>
</TD>
</TR>

<TR>
<TD><A NAME="pctD"></A>%D0 or %D </TD>

<TD ROWSPAN=4>Data compression </TD>

<TD>512 BLTZ dictionary size<BR>
</TD>
</TR>

<TR>
<TD>%D1 </TD>

<TD>1024 BLTZ dictionary size<BR>
</TD>
</TR>

<TR>
<TD>%D2 </TD>

<TD>2048 BLTZ dictionary size<BR>
</TD>
</TR>

<TR>
<TD>%D3 </TD>

<TD>4096 BLTZ dictionary size<BR>
</TD>
</TR>

<TR>
<TD><A NAME="pctE"></A>%E0 or %E </TD>

<TD ROWSPAN="6">Escape method </TD>

<TD>ESCAPE DISABLED<BR>
</TD>
</TR>

<TR>
<TD>%E1 </TD>

<TD>+++AT method (default)<BR>
</TD>
</TR>

<TR>
<TD>%E2 </TD>

<TD>&lt;BREAK&gt;AT method<BR>
</TD>
</TR>

<TR>
<TD>%E3 </TD>

<TD>BOTH methods enabled<BR>
</TD>
</TR>

<TR>
<TD>%E4 </TD>

<TD>Disable &quot;OK&quot; to +++<BR>
</TD>
</TR>

<TR>
<TD>%E5 </TD>

<TD>Enable &quot;OK&quot; to +++<BR>
</TD>
</TR>

<TR>
<TD><A NAME="bsJ"></A>\J0 or \J </TD>

<TD ROWSPAN=2>DTE Auto Rate Adjustment </TD>

<TD>Disabled<BR>
</TD>
</TR>

<TR>
<TD>J1 </TD>

<TD>DTE rate is adjusted to match carrier rate.<BR>
</TD>
</TR>

<TR>
<TD><A NAME="bsN"></A>\N0 or \N </TD>

<TD ROWSPAN=8>Connection type </TD>

<TD>Normal connection (see below for definitions)<BR>
</TD>
</TR>

<TR>
<TD>\N1 </TD>

<TD>Direction connection<BR>
</TD>
</TR>

<TR>
<TD>\N2 </TD>

<TD>MNP Auto-reliable connection<BR>
</TD>
</TR>

<TR>
<TD>\N3 </TD>

<TD>Auto-reliable connection<BR>
</TD>
</TR>

<TR>
<TD>\N4 </TD>

<TD>V.42bis reliable link with phase detection<BR>
</TD>
</TR>

<TR>
<TD>\N5 </TD>

<TD>V.42bis auto-reliable link with phase detection<BR>
</TD>
</TR>

<TR>
<TD>\N6 </TD>

<TD>V.42 reliable link with phase detection<BR>
</TD>
</TR>

<TR>
<TD>\N7 </TD>

<TD>V.42 auto-reliable link with phase detection<BR>
</TD>
</TR>
</TABLE>

<P><B>Note:</B> A <I>direct connection</I> is a simple straight-though
connection without any error correction or data compression. In this case,
the computer-to-modem and modem-to-modem speeds must be identical.</P>

<P>A <I>normal</I> connection uses flow control (either software or hardware)
to buffer the data being sent or received, so that the modem can transmit
data at a different rate than the computer is actually sending or receiving
it. For example, a computer may send actual data at 57kbps, but using compression,
the modem only actually sends 28.8kbps. This is the mode use by most modems.</P>

<P>A <I>reliable</I> connection is a type of normal connection; if, for
some reason, data compression or error correction cannot be established
or maintained, the connection will hang up. (In essence, such a modem ensures
that all connections are reliable, for it will hang up if the connection
isn't.)</P>

<P>Likewise, an <I>auto-reliable</I> connection is virtually the same,
except that the modem will try to renegotiate the connection in order to
establish a reliable connection. Again, this is the mode that most modems
use.</P>

<P>
<HR SIZE=1 NOSHADE></P>

<H2><A NAME="sregister"></A>S-Registers:</H2>

<TABLE BORDER=1 WIDTH="100%" >
<TR>
<TH>Register </TH>

<TH>Range </TH>

<TH>Default </TH>

<TH>Function<BR>
</TH>
</TR>

<TR>
<TD><A NAME="S0"></A>S0 </TD>

<TD>0-255 rings </TD>

<TD>1-2 </TD>

<TD>Answer on ring number Don't answer if 0<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S1"></A>S1 </TD>

<TD>0-255 rings </TD>

<TD>0 </TD>

<TD>If S0&gt;0 this register counts incoming rings<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S2"></A>S2 </TD>

<TD>0-127 ASCII </TD>

<TD>43 + </TD>

<TD>Escape to command mode character <BR>
</TD>
</TR>

<TR>
<TD>S2 </TD>

<TD>&amp;gt;127 </TD>

<TD></TD>

<TD>no ESC<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S3"></A>S3 </TD>

<TD>0-127 ASCII </TD>

<TD>13 CR </TD>

<TD>Carriage return character<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S4"></A>S4 </TD>

<TD>0-127 ASCII </TD>

<TD>10 LF </TD>

<TD>Line feed character<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S5"></A>S5 </TD>

<TD>0-32,127 ASCII </TD>

<TD>8 BS </TD>

<TD>Backspace character <BR>
</TD>
</TR>

<TR>
<TD><A NAME="S6"></A>S6 </TD>

<TD>2-255 seconds </TD>

<TD>2 </TD>

<TD>Dial tone wait time (blind dialing, see Xn)<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S7"></A>S7 </TD>

<TD>1-255 seconds </TD>

<TD>30-60 </TD>

<TD>Wait time for remote carrier<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S8"></A>S8 </TD>

<TD>0-255 seconds </TD>

<TD>2 </TD>

<TD>Comma pause time used in dialing<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S9"></A>S9 </TD>

<TD>1-255 1/10 sec. </TD>

<TD>6 </TD>

<TD>Carrier detect time required for recognition<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S10"></A>S10 </TD>

<TD>1-255 1/10 sec. </TD>

<TD>7-14 </TD>

<TD>Time between loss of carrier and hangup<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S11"></A>S11 </TD>

<TD>50-255 millisec. </TD>

<TD>70-95 </TD>

<TD>Duration and spacing of tones when tone dialing<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S12"></A>S12 </TD>

<TD>0-255 1/50 sec. </TD>

<TD>50 </TD>

<TD>Guard time for pause around +++ command sequence<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S36"></A>S36 </TD>

<TD>Fallback options when error correction link fails:<BR>
0 - Disconnect<BR>
1 - Establish Direct connection<BR>
3 - Establish Normal connection<BR>
4 - Establish a MNP connection if possible, else Disconnect<BR>
5 - Establish a MNP connection if possible, else Direct connection<BR>
7 - Establish a MNP connection if possible, else Normal connection<BR>
</TD>

<TD>7 </TD>

<TD>Negotiation Failure Treatment<BR>
</TD>
</TR>

<TR>
<TD><A NAME="S37"></A>S37 </TD>

<TD>1 = 300 bps<BR>
5 = 1200 bps<BR>
6 = 2400 bps<BR>
7 = 1200/75 bps (v.23 mode)<BR>
8 = 4800 bps<BR>
9 = 9600 bps<BR>
10 = 12000 bps<BR>
11 = 14400 bps<BR>
12 = 7200 bps </TD>

<TD>0 </TD>

<TD>Negotiation Speed (Initial handshake)<BR>
</TD>
</TR>
</TABLE>

<P>Many modems have dozens, even hundreds, of S registers, but only the
first dozen or so are fairly standard. They are changed with a command
like <A HREF="#S">ATSn=N</A>, and examined with <A HREF="#S">ATSn?</A>
(e.g. &quot;<A HREF="#S10">AT S10=70</A> <A HREF="#S">S1?</A>&quot; would
tell the modem not to hang up for seven seconds should it not hear the
answering modem, and return the number of times the phone last rang.)</P>

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