
          B A S I C   A T   C O M M A N D S
          
          The standard AT command set is sometimes referred to as
          Hayes compatible modem commands. A modem that is Hayes
          compatible can use this standard Hayes command set. 
          Don't buy a modem if it isn't Hayes compatible. Almost
          all modems sold today support these AT commands. The
          command letters AT wake up the modem and initialize it. 
          The AT means ATTENTION modem. This list of commands is
          for reference only; please don't feel you need to memorize
          them! If you do, your cohorts will presume you're a nerd
          (and correctly so).
          
          COMMAND        FUNCTION
          
          A/         Repeats the last AT command (this command does
                     not need to be preceded by the letters AT)
          +++        Switches the modem from online mode to command
                     mode (this command does not need to be preceded
                     by the letters AT)
          
          AT         Attention modem--(wakes up the modem)
          
          
          
          
          The following commands require an AT to precede the
          command (such as ATA for the first one on the list):
          
          A          Sets the modem in answer mode
          DT         Dials a touch-tone phone
          DP         Dials a pulse (rotary) phone                           
          
          
                 dial modifiers
                     
                 R       Originate call in answer mode (to call
                         originate only modems)
                 S=n     Dial the stored numbers where n= 0,1,2,3
                 W       Wait for dial tone prior to dialing--the time
                         period of the pause is determined by an S
                         register setting
                 ,       Pause 2 seconds before continuing to dial
                 /       Pause .125 second before continuing to dial
                 ;       Remain in command mode after connection
                 !       Flash hook--hangs up then reconnects in .5
                         second
                 @       Wait for silence before continuing to dial--the
                         time period of the pause is determined by an S
                         register setting
          
          
          COMMAND        FUNCTION

          E or E0    Turns character echo off
          E1         Turns character echo on
          F or F0    Sets modem to half-duplex
          F1         Sets modem to full-duplex
          H or H0    Hangs up the phone
          I or I0    Shows the modem product code
          I1         ROM check
          I2         ROM test
          L1         Sets modem speaker volume to low
          L2         Sets modem speaker volume to medium
          L3         Sets modem speaker volume to high
          M2         Turns modem speaker on for the entire connection
                     (don't do it!)
          M0         Turns modem speaker off
          M1         Turns modem speaker off when connection is
                     established
          O0         Returns online after entering command mode
          Q0         Turns on result code display
          Q1         Turns off result code display
          Sxn        Sets the S register x to the value of n; note
                     that both x and n are variable numbers 
          Sx?        Displays value of register Sx                              
          V0         Sets modem to display numeric result codes 
          V1         Sets modem to display verbose codes (words)
          Xn         Modem response sets (note that n is a variable
                     number)
                     X0=minium responses
                     X1=minium responses--don't wait for dialtone
                     before dialing
                     X2=like X1 but do wait for dialtone before
                     dialing
                     X3=like X1 but adds call progress messages and
                     tone detection
                     X4=call progress messages--tone detection and wait
                     for dialtone                             
          Z          Resets modem                             
          &          Advanced commands prefix (not all modems support
                     these)
          &F         Resets modem to factory default                 
          
          
          S REGISTERS
          
          A Hayes compatible modem has special memory locations
          called S registers. A modem initialization string
          consists of AT commands which usually include S register
          settings. The list below gives some of the more
          important S register functions.    
          
                         FUNCTION
          
          S0         Sets the number of rings to answer when in auto
                     answer mode.
                     S0=0 (which is usually the default setting)
                     suppresses auto answer. S0=3 sets the modem to
                     auto answer mode and tells the modem to answer on
                     the third ring.
          
          S1         Counts the number of rings from an incoming call
                     and stores it.
          S2         Stores the ASCII escape code character.
          S3         Stores the ASCII decimal code for a carriage
                     return.
          S4         Stores the ASCII decimal code for a line feed.
          S5         Stores the ASCII decimal code for a backspace.
          S6         Sets the time in seconds that a modem waits
                     before dialing.
          S7         Sets the time in seconds, that a modem waits for
                     a carrier. If you desire to make an
                     international call you might want to change this
                     to a longer time period.
          S8         Sets the time in seconds, for a comma pause.  The
                     default for a (,) pause is usually set to 2
                     seconds.
          S9         Sets the time in 1/10 seconds for carrier detect
                     response
          S10        Sets the time in 1/10 seconds for lost carrier
                     hang-up delay.
          S11        Sets the touch-tone dialing duration and spacing
                     in milliseconds.
          S12        Sets the time in 1/50 seconds for the Hayes
                     escape code guard time.
          S13        Bit-mapped register for UART.
          S14        Bit-mapped option register.
          S15        Bit-mapped option for flag register.
          S16        Modem self-test.
          S28        Sets the time in 1/10 seconds for V.32 answer
                     tones.  
          

          AT COMMAND SET USAGE
          
          AT commands need to be issued in upper or lower case
          letters. You can't mix upper and lower case letters when
          issuing an AT command. When loaded, most
          telecommunications programs start in the command mode. 
          This means you can issue AT commands from the keyboard as
          soon as you load your telecommunications program. Try
          loading yours. Then type:
          
                                atz <ENTER>
          
          If your modem is connected to the serial port you
          designated when you set up your telecommunications
          software and it is working properly, you should see OK on
          your screen.
          
          OK
          
          Next, you can try dialing a BBS number using an AT
          command. If you have a touch-tone phone (most people
          do), try issuing a command while in the command mode of
          your telecommunications program:
          
                                atdt845-8532 <ENTER>
          
          The dashes are optional. Suppose you were at a phone
          where you had to dial 9 before you got an outside line. 
          Start up your telecommunications software, then from the
          command mode type:
          
                                at dt 9 , 845-8532 <ENTER>
          
          In this example spaces were used. AT commands ignore
          spaces and dashes. The first AT command got the modem's
          attention. The following DT told it to dial using touch-
          tone dialing. The 9 is to get an outside line.  A comma
          then instructs the modem to pause two seconds before
          continuing (see the dial modifiers in the basic AT
          commands). The 845-8532 is the phone number you want to
          dial. Note that you only need the AT (attention modem)
          at the beginning of an AT command statement and that AT
          commands can be strung together.
          
          Perhaps you have a burning desire to check the value of
          your S7 register. This will show the number of seconds
          that your modem waits for a carrier before hanging up. 
          Start up your telecommunications software, then from the
          command mode type:
                 
                                at s7? <ENTER>
          
          The above command will show you the value of your modem's
          S7 register.

          Your telecommunications software manual will probably
          mention the modem initialization string. This is the
          string of commands that initializes your modem. The AT
          command section combined with the S registers section
          should help you understand your modem's initialization
          string. See your particular modem manual for more
          details on AT commands and initialization strings. 
          Different modems require different modem initialization
          strings. The better telecommunications software programs
          will have a modem pick-list feature. With such a
          feature, the software will automatically set your modem
          for optimum use with pre-defined setup initialization
          strings. When newer modems come out, telecommunications
          software manufactures have to keep adding the new modems
          to their pick-list. If your modem is not on their pick-
          list, you can often contact the company that makes the
          telecommunications program for a software update. For
          example, if you are using Telix, you would contact
          deltaComm Development, the company that makes Telix. 
          Many of these companies maintain a BBS where customers
          can download updates.    
          
          You can also send AT commands to your modem from the DOS
          command line. Suppose you have your modem connected to
          COM2 (serial port) and a speaker phone connected to your
          modem. Go to the DOS prompt. With your modem on, you
          can dial a number by using the ECHO command. First,
          press the button to activate your speaker phone. Then,
          at the DOS prompt type:
          
                                echo atdt845-8522 >com2 <ENTER>
          
          That's dialing from DOS!  
          
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