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Chapter 3 - Basic Modem Operation
3-4
Quick Tips when issuing AT Commands
The ENTER or RETURN key must be pressed to execute a command.
Multiple AT commands can be combined into one line. For example,
AT&D2 and AT&N0 can be combined into one line AT&D3&N0.
The Omni 288S 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.
If you see duplicated characters for each one you type, your Omni 288S and
software both have their “echo” feature turned. The Omni 288S 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.
When a command is successfully issued and accepted, a modem responds
with what is called a “Result Code.” The Omni 288S 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
A> Repeats the last issued AT command once, or re-dials
the last dialed number up to 9 times until a key is
pressed or a connection is made.
<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 Omni 288S 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*I1