AT commands
Digi TransPort User Guide 118
Escape sequences
If you enter a command such as ATD, which results in the router successfully establishing a
connection to a remote system, it will issue a CONNECT result code and switch from command
mode to on-line mode. This means that it will no longer accept commands from the terminal.
Instead, data will be passed transparently through the router to the remote system. In the same
way, data from the remote system will pass straight through to your terminal.
The router will automatically return to command mode if the connection to the remote system is
terminated.
To return to command mode manually, you must enter a special sequence of characters called
the escape sequence. This consists of three occurrences of the escape character, a pause (user
configurable) and then AT. The default escape character is + so the default escape sequence is:
+++ {pause} AT
Entering this sequence when the router is on-line will cause it to return to command mode but it
will NOT disconnect from the remote system unless you specifically instruct it to do so (using ATH
or another method of disconnecting). If you have not disconnected the call, the ATO command
may be used to go back on-line.
AT command result codes
Each time an AT command line is executed, the router responds with a result code to indicate
whether the command was successful. If all commands entered on the line are valid, the OK
result code will be issued. If any command on the line is invalid, the ERROR result code will be
issued.
Result codes may take the form of an English word or phrase (verbose code) or an equivalent
number (numeric code), depending on the setting of the ATV command. Verbose codes are used
by default.
The ATV0 command can be used to select numeric codes if required. The results from the text
based commands can be numeric or verbose. A full list of the Result codes is provided in the
following table:
Numeric Code Verbose Code Meaning
0 OK Command line executed correctly
1 CONNECT ISDN connection established
2 RING Incoming ring signal detected
3 NO CARRIER X.25 service not available
4 ERROR Error in command line
6 NO DIALTONE ISDN service not available
7 BUSY B-channel(s) in use
8 NO ANSWER No response from remote
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