Ford Explorer 2008 Owner's Manual page 65

Entertainment Systems
Your FES system is equipped with
two sets of battery powered,
infrared wireless headphones. Two
AAA batteries are needed to operate
the headphones. (Batteries are
included.)
Additional infrared wireless
headphones may be purchased for
use with the system. Also, wired
headphones may be purchased and
plugged in where indicated on the
left and right hand sides of the
system. Refer to Wired
Headphones following.
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