FORD 2005 Grand Marquis - Manual (Page 16)

Headphones
Wireless headphones
Your FES system is equipped with two sets of battery powered, infrared
wireless headphones. Power and volume controls are located on the
headset.
Additional headphones may be purchased and plugged in forward of the
LCD screen. Refer to Wired Headphones below.
2005 (dvd)
Supplement
USA_English (fus)
System Descriptions
16