ZyXEL Communications U-336SA - Manual (Page 33)

Basic Modem Operation 19
Modem Result Codes
When you execute or try to execute an AT command, your modem
sends a result code to let you know whether the command was
executed. An OK result code means the AT command you sent was
executed. If you receive an ERROR code, it means the command was
invalid.
The U-336S/SA also provides result codes that show:
•
Whether or not a Dial Tone was detected when the modem
originated a call.
•
If a busy signal was detected when the modem originated a call.
•
If a remote telephone ring was detected when dialing.
•
The speed, protocol, and error control/data compression method
used.
•
If your modem has detected an incoming ring.
Result codes can originate from any of eight result code sets. The
ATXn command lets you choose which set of result codes your
modem uses. By default, your modem uses result codes equivalent to
the ATX5 command.
The result code options will be covered more thoroughly in later
chapters.
Viewing S Register Values
Status registers (or "S -registers") contain values that determine the
modem’s operating characteristics. Whenever you send an AT
command to your modem, you are actually changing the value of an S-
register.