Sennheiser Set 820 Instruction Manual page 25

WARNING: Volume up? - No!
When people use headphones, they tend to choose a higher volume than
with loudspeakers. However, if your hearing has deteriorated and you need
to rely on an assitive listening system, please avoid listening at high volume
levels for a long time. Please protect your hearing.
ATTENTION: Danger of short circuit!
Neither transmitter nor receiver must get wet or excessively moist, e.g. due
to spilled liquids or use in damp rooms.
ATTENTION:
Components from other manufacturers (e.g. for power supply or battery)
may cause damage to the unit and will invalidate the warranty.
This advice complies with Part 15 of the FCC Rules and with RSS-210 of
Industry Canada. Operations is subject to the following two conditions:
(1) this device may not cause harmful interference, and
(2) this device must accept any interference received, indcluding
interference that may cause undesired operation.
FCC ID: DMOUSC820
IC: 2099A-USC820
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