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Introduction to Modem Operation-The AT Command Set
RC3000A modules are used to originate or answer telephone calls and establish links
with other devices for the purpose of transmitting voice, data, or fax information between
two locations. Please refer to the SIM900 AT Command Manual for complete AT
command listings and information
After installation, you will now be able to communicate with the modem and establish
connections with remote devices. Controlling the modem functions is accomplished by
using “AT” commands. These commands are used to instruct the modem to perform
functions such as dialing or to answers calls. These commands are normally
automatically issued by communication software. However for some applications,
custom software may have to be written due to the absence of a normal operating system
such as DOS or Windows.
NOTE: The first AT command issued must be Upper Case AT. Subsequent AT
commands can be either Upper Case or Lower Case.
The modem will automatically accept and process “AT” commands at most standard
DTE (Data Terminal Equipment) speeds and parity settings. For each command issued,
the modem will respond with a result code informing you of the modem’s status. The
format of a basic “AT” command and result code is as follows:
AT <Command> <CR>
OK
AT = ATtention what follows is a command
<Command> = any valid command
<CR> = Carriage Return or Enter Key
OK = Result code meaning: the modem has accepted the command
AT Commands Samples
A. General Commands
Syntax
Expect Result
Description
1
ATI
Display product identification
information.
2
AT+CGMI
Request manufacturer identification.
3
AT+CGMM
Request model identification.
4
AT+CGMR
Request revision identification.
5
AT+CGSN
Request product serial number