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AT Commands
Page 31
Appendix A
AT Commands
Syntax and Procedures
The command and response syntax and procedures generally conform to referenced
recommendations and standards. Since these recommendations and standards describe
characteristics universal to a large installed base of modems to a maximum degree, there may be
syntax and procedural differences due to extensions and behavioral differences in implemented
commands, parameters, and responses beyond that described in these recommendations and
standards.
The syntax and procedures described in this appendix are based on V.250 and V.253 with
additional information included for implemented extensions, behavioral differences beyond V.250,
and legacy commands.
Alphabet
The T.50 International Alphabet 5 (IA5) is used in this document. Only the low-order seven bits
of each character are significant to the modem; any eighth or higher-order bit(s), if present, are
ignored for the purpose of identifying commands and parameters. Lower-case characters are
considered identical to their upper-case equivalents when received by the modem from the DTE.
Result codes from the modem are in upper case.
DTE Commands Lines
Words enclosed in <angle brackets> are references to syntactical elements. The brackets are not
used when the words appear in a command line, the brackets are not used. Words enclosed in
[square brackets] represent optional items which may be omitted from the command line at the
specified point. The square brackets are not used when the words appear in the command line.
Other characters that appear in syntax descriptions must as included as shown. Any modem
responses are mentioned in terms of their alphabetic format; the actual response issued will
depend on the setting of parameters that affect response formats, e.g., Q and V commands (see
2.7).