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APPENDIX A: AT INTERFACE
A.1 Command Types
The A3LA-RM employs two principal types of AT commands: basic and extended. The two types have
differing syntax used to query and adjust their settings. They also have unique reference standards. A
specific basic AT command is used to reference S-registers and query and adjust their settings. Its syntax is
similar to that of extended AT commands.
A.2 Basic Commands
Basic commands are industry standard and originally developed for Hayes-compatible PSTN modems. In
many cases, basic commands consist of a single ASCII alpha character. In other cases, a special character
precedes the alpha character. Prefix characters used in A3LA-RM basic commands include &, \, %, and *.
Most alpha characters in basic commands are followed by a numeric parameter, n. To adjust its setting,
a basic command is entered with the appropriate numeric value of n. Note that if the numeric parameter n is
omitted from the basic command entry, a value of zero is assumed for n. For example, ATXn is set to a
value of 4 by entering ATX4, whereas it is set to value of 0 by entering either ATX0 or ATX.
To query a basic command setting, the AT&V command is entered to view the active configuration of a
group of basic commands. Some basic commands listed in this document are marked with “No action,
compatibility only”. In these cases, the basic command is accepted in the same fashion as is with other
modems, but has no effect on the operation of the A3LA-RM, since it has no meaning in the Iridium
environment.
A.3 Extended Commands
Extended commands perform actions or set parameters that extend the capability of the A3LA-RM
beyond that which is allowed by basic commands. In some cases, they were designed for non-PSTN
networks, such as the GSM network.
Most extended commands include a prefix of + followed by a single alpha character. Prefixes used in
A3LA-RM extended commands iC, +D, +G, +I, and +S. Extended commands designed specifically
for Iridium products include a –MS prefix. Most extended commands include three alpha characters after the
prefix, but some commands include just one or two alpha characters after the prefix.
Some extended commands have a single execution mode. No further syntax is added after the prefix
and body of the command. For example, AT+GSN is entered as shown to query the A3LA-RM for its
assigned serial number (i.e. IMEI). Some extended commands incorporate a test mode to query their range
of valid responses. Some extended commands incorporate set, read, and test modes. For example, AT–
MSVTR is entered as AT–MSVTR=n in set mode to enable/disable receipt of DTMF messages. It is entered as
AT–MSVTR? in read mode to query its current setting and is entered as AT–MSVTR=? in test mode to query
its range of valid settings. Extended commands are grouped as shown below.
Extended Cellular Commands:
+C prefix
Used for GSM cellular phone-like functions
Standards: ETSI specifications GSM 07.07 [2] and GSM 07.05 [3]
Extended Data Compression Commands:
