China Aerospace Telecommunications Ltd
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2.3 Working mechanism of data transparent transmission
Any data not being above-mentioned parameter format that terminal serial port received will
be considered as "user transparent transmission data", and according to channel status, data
will be sent to its destination by GPRS data link or Iridium SBD.
Bytes interval in the data packet of "user transparent transmission data" should not be larger
than 0.5 second and the length of each data packet should not be larger than 336 bytes. When
large amounts of data need to be transmitted, data will be divided into packets.
Data transmission between terminals has a data length limit with a maximum of 266 bytes.
As a response, after sending "user transparent transmission data", device then sends a "SEND
OK" message to external data device via serial port. After external data device receives this
response, it prepares to send next data packet.
In dual-mode communication, GPRS channel has priority. If condition meets < login failed or
heartbeat confirmation failed, reboot GPRS link connection, if failed, wait 30 seconds, then
again, if still failed after three times>, it will automatically switch to Iridium SBD
communication channel. In Iridium SBD communication channel mode, system still keep
booting GPRS link connection until connecting successfully, if connected, communication
mode turns to GPRS communication channel.
2.4 LED indicator for working status
2.4.1 GSM status
Blinking: GPRS network login success.
Always light: Do not login to GPRS network yet.
Turn off: sleep status, GSM does not work or GSM fault.
2.4.2 GPS status
Blinking: GPS positioned successfully.
Always light: searching signal.
Turn off: sleep status, GPS does not work or GPS fault.
2.4.3 Iridium network
Blinking: Iridium is in network service status.
Always light: Iridium is not in network service status.
Turn off: sleep status, Iridium does not work or Iridium fault.
2.4.4 Iridium sending status
Blinking: Iridium is receiving or sending data.
