11
Chapter 2
How Modem Mode
2.1 DIALING OUT
When the mobile computer is seated in the cradle, it can send the collected data back to
a remote server, as well as download lookup files, via GSM or 3G/GPRS.
When dialing out (
ATDT
), the LED of LAN will flash at the time interval of 0.3 seconds for
20 seconds. When connected, the LED of LAN will become green after successfully
establishing a connection. The LED of TX/RX will flash as long as data transmission
occurs.
Note: It is suggested to issue the command “
AT
” every five seconds for best practice, in
order to check whether the mobile computer is seated in the cradle.
The escape sequence, consisting of three characters “
+++
”, is used to terminate
the data connection.
2.1.1 GSM CONNECTION
When initialization is done, issue
ATDT
(phone number) to establish data connection via
GSM.
Note: GSM support is dependant on your Network operator and your ISP. Typically GSM
is used with 2G SIM cards.
2.1.2 3G/GPRS CONNECTION
When initialization is done, issue
ATDT
xxx.xxx.xxx.xxx:kkkk or
ATDT
[HostName:Port] to
establish data connection via 3G/GPRS. The buffer size of the cradle is 1460 bytes, and
data packet will be sent out as long as it satisfies any of the following requirements:
buffer is full (= maximum packet size is 1460 bytes)
delimiter character is encountered
end of transmission timeout (= no transmission for 5 milliseconds)
