La Crosse Technology WS-7136U Instruction Manual page 6

In this time the indoor temperature station
and remote temperature sensor will start to
talk to each other and the display will show
both the indoor temperature and an outdoor
temperature. If the indoor temperature
station does not display both the indoor
temperature and the outdoor temperature
after the 15 minutes please retry the set up as
shown on page five.
After both the indoor temperature and
outdoor temperature are displayed for 15
minutes you can place your remote
temperature sensor outdoors and set your
time.
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