Huawei YAL-L21 Quick Start Manual page 13

--Connect the equipment into an outlet on a circuit different
from that to which the receiver is connected.
--Consult the dealer or an experienced radio/TV technician for
help.
This device complies with Part 15 of the FCC Rules. Operation
is subject to the following two conditions: (1) this device may
not cause harmful interference, and (2) this device must accept
any interference received, including interference that may
cause undesired operation.
Caution: Any changes or modifications to this device not
expressly approved by Huawei Technologies Co., Ltd. for
compliance could void the user's authority to operate the
equipment.
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