La Crosse Technology WS-7208TWC Instruction Manual page 4

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 temperatures after the 10
minutes please retry the set up as stated
above. After both indoor and outdoor
temperatures are displayed for 10
minutes you can place your remote
temperature sensor outdoors and set your
time.
The remote temperature sensor should be
placed in a dry, shaded area. The remote
temperature sensor has a range of 80
feet. Any walls that the signal will have
to pass through will reduce distance. An
outdoor wall or window will have 20 to
30 feet of resistance and an interior wall
will have 10 to 20 feet of resistance.
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