Milesight EM300 Series, User Manual, Page: 16 / 26

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3.5.4 Data Retransmission
EM300 series sensor supports data retransmission to ensure network server can get all data
even if network is down for some times. There are two ways to get the lost data:

Network server sends downlink commands to to enquire the historical data for specifying
time range, see section
5.4 ;

When network is down if no response from LinkCheckReq MAC packets for a period of time,
the device will record the network disconnected time and re-transmit the lost data after
device re-connects the network.
Here are the steps for data retransmission:
1. Ensure the device time is correct (see section
3.4 );
2. Enable data storage feature and data retransmission feature;
3. Go to Device > Setting > General Settings to enable rejoin mode feature and set the number of
packets sent. Take below as example, the device will send LinkCheckReq MAC packets to the
network server at least every 30 minutes to check if the network is disconnected; if there is no
response for 8 times (8 * 30 mins = 240 mins =4 hours), the device will record a data lost time
point (disconnected time minus 4 hours).