Sennheiser RI 150 Instructions For Use Manual page 14

FREE LINE OF SIGHT
Infra-red light is transmitted in the same way as the light from a light bulb. Do
not obstruct the path of the light between the transmitter and the receiver, and
stay in the room where the transmission is taking place!
Make sure that you wear the stethoset receiver the right way round,
with the "Sennheiser" logo at the front.
There is a simple rule: If you can see the transmitter or the infra-red radiator
from where you are, transmission can take place without any interference.
VOLUME UP? - NO!
When people use headphones, they tend to choose a higher volume than with
loudspeakers. Listening at high volume levels for long periods can lead to
permanent hearing defects. Please protect your hearing, Sennheiser headphones
have an excellent sound quality even at low volumes.
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