All AT commands must be followed by a carriage return.
Send one command at a time to SpeedyDialer.
A carriage return (end of command) will flash the Status LED on SpeedyDialer.
Ring is always enabled while in the monitor loop waiting for a command.  Speedy
Dialer will send "RING" to the PC whenever a ring is detected.
ATH              Go On Hook (Hang up the phone).
ATH1            Go Off Hook (Pick up the phone).
ATD              Dial a number using DTMF dialing.  Does not take off hook.
ATI0               Returns device serial number.
ATI1               Returns device firmware software version.
ATZ               Resets the SpeedyDialer micro-processor - 2 second delay.
AT*S+or-nn  Adjust headset speaker volumn.
AT*M+or-nn  Adjust headset microphone volumn.
AT*X0       PC Card line out directed to the SpeedyDialer Inputs.
 or
AT*X1       PC Card line out directed to the external speaker jack.
AT*C0 = off Call Progress Mode.
AT*C1 = on  Sends DTMF at slow speed.  Can't decode DTMF's.  Detects call progress
               tones.  Responses:Busy,Reorder,Ringback,Continuous Tone,Voice??
               or
AT*D0 = off DTMF Mode.
AT*D1 = on  Sends DTMF at fast speed.  Decodes DTMF's.  Can't detect call progress
               tones.  Responses: Sends single bytes to PC 1,2,3,4,5,6,7,8,9,*,0,#.

All AT registers:
ATS*n?     causes SpeedyDialer to send the current value.
ATS*n=     followed by new value 01 to 99 sets new value in SpeedyDialer.
ATS*2       Silence Detection Period in seconds. 01 to 99 secs.
ATS*3       Flash Interval Period ten msecs. Enter 01 to 99 = .010 to .990 msecs.

Dial String Modifiers:  These can be placed anywhere in the string.
 ","       Inserts a 1 second delay in dialing.
 "!"       Inserts a switchhook "flash" into the dialing sequence.
           *Note - Goes on hook for ats*3 * 10 msecs - then back off hook.
 "/"       slash inserts a .1sec pause in dialing.
 @       Silence detection period adjusted by ats*2.  Used in dial string and
           also determines when "silent" message will be sent during Call
           Progress Monitoring.
 W       Waits for dial tone before continuing.  Response "Dial Tone" or "No Dial
          Tone ".  Automatically puts in Call Progress Mode to detect dial tone and "
          returns to whatever user had set previously.
 F       Fast Dial 51msec on - 51msec off.  Remembers all previous Mode settings.
 S      Slow Dial Default 102msec on - 102msec off.  Remembers Mode settings.