ZyXEL Communications COMET 336, User Manual

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Basic Modem Operation 17
The Comet 336 processes commands from left to right. The AT command that appears
to the right might over-write the command to the left if they are trying to accomplish
tasks or set modes that cannot coexist.
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If you see duplicated characters for each one you type, your Comet 336 and
software both have their “echo” feature turned. The Comet 336 command echo state
is switched off using ATE0 and on using ATE1 (default). To eliminate the double
characters, turn off the software’s command echo rather than using the ATE0
command. If you see no characters in your terminal window when you type, the
modem’s echo setting is probably set to off. In this case, issue the ATE1 command.
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When a command is successfully issued and accepted, a modem responds with
what is called a “Result Code.” The Comet 336 supports both “verbose” result
codes (i.e. “OK”), and “numerical” result codes (i.e. “0").
You can use the ATV command to set it one way or the other as follows:
Command Description
ATV0 Select numerical result code
ATV1 Select verbose result code
There are a few basic commands that do not require the “AT” command prefix. These
are as follows:
Command Description
A/ Repeats the last issued AT command once
<any key> Terminates the current connection attempt, if pressed
while modem is handshaking.
+++ Escape code sequence. Entered while the modem is in
Data Mode. Returns modem to Command Mode.
The Comet 336 supports several groups of AT commands:
AT Command Set/Type Example
Basic AT (Hayes compatible) ATB0
Basic AT$ (on line help) AT$
Extended AT& commands AT&N0
Extended AT* commands AT*E0
Fax and Voice AT+ commands AT+FCLASS=2
S-Register command ATS0=1
S-Register inquiry command ATS0?
You may browse the lists of available commands for each command set by using the on-
line help commands: AT$, AT*$, AT&$, and ATS$. Further detail on AT commands
will be covered in the chapters that pertain to their uses.