Panasonic TC-55CX400U Owner's Manual page 14

HDMI connection is available if connected audio equipment has ARC (Audio Return Channel) function.
Panasonic does not guarantee operation and performance of peripheral devices made by other
manufacturers; and we disclaim any liability or damage arising from operation and/or performance from usage
of such other maker's peripheral devices.
14
Audio Connection
Optical cable
HDMI cable
DIGITAL
AUDIO IN
e.g. Amplifier with
speaker system
HDMI OUT
(ARC)