FORD 2010 F-550 v.2 - Manual (Page 20)

Parking brake on warning chime: Sounds when the parking brake is
set, the engine is running and the vehicle is driven more than 3 mph
(5 km/h). If the warning remains on after the parking brake is off,
contact your authorized dealer as soon as possible.
Turn signal chime: Sounds when the turn signal lever has been
activated to signal a turn and not turned off after the vehicle is driven
more than 2 miles (3.2 km).
Message center activation chime: Sounds when some warning
messages appears in the message center display for the first time.
Overspeed chime (if equipped): Sounds when the vehicle speed
reaches 75 mph (120 km/h) or higher.
Airbag secondary warning chime: Sounds to inform the driver, in the
event that the airbag readiness warning lamp is inoperable, that there is
a fault in the supplemental restraint system.
GAUGES
Speedometer: Indicates the current vehicle speed.
Instrument Cluster
20
2010 F-250/350/450/550 (f23)
Owners Guide, 2nd Printing
USA (fus)