La Crosse Technology WT-5120 Instruction Manual page 24

1. The distance of the projection alarm clock or transmitter should be at least 2
metres away from any interfering sources such as computer monitors or TV sets.
2. Avoid placing the transmitter onto or in the immediate proximity of metal window
frames.
3. Using other electrical products such as headphones or speakers operating on the
868MHz-signal frequency may prevent correct signal transmission or reception.
Neighbors using electrical devices operating on the 868MHz-signal frequency
can also cause interferences.
Note:
When the 868MHz signal is received correctly, do not re-open the battery cover of
either the transmitter or projection alarm clock, as the batteries may spring free from the
contacts and force a false reset. Should this happen accidentally then reset all units
(see "Setting up" above) otherwise transmission problems may occur.
The transmission range is around 100 metres from the temperature transmitter to the
projection alarm clock (in open space). However, this depends on the surrounding
environment and interference levels. If no reception is possible despite the observation
of these factors, all system units have to be reset (see "Setting up" above).
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