La Crosse Technology WIRELESS WEATHER STATION Instruction Manual page 10

7. Insert the batteries to the third transmitter immediate after (in 10 seconds
after) inserting battery to the second transmitter.
8. Then within 2 minutes, the channel 3 outdoor data from the third transmitter
will be displayed and the channel icon will shift back to "1" once the third
transmitter is successfully received. If this is not happen, user shall restart
the setting up from step 1.
Note:
After the three transmitters have been set up, user may need to check the
readings displayed on the weather station against those being shown on the
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