b. Used for connecting the intervehicular hoses from
the towing vehicle to the semitrailer.
c. After connection of hoses, the service brakes on
the semitrailer can be controlled by the brake controls
on the towing vehicle.
d. Located on front cross-member of the chassis
a. Two dummy couplings to be fitted to the
SERVICE and EMERGENCY air hose couplings.
b. Connected when brake air hose couplings are not
connected to the towing vehicle.
c. Used to prevent dirt and moisture from entering
the braking system.
d. Chained to brackets welded to the front cross-
member of the chassis frame.
Figure 2-7. Dummy couplings
Wear protective goggles when opening
air reservoir drain cock and avoid
contact with high velocity air.
a. Used to relieve air pressure in the semitrailer
b. Used for drainage of moisture collected in brake
Figure 2-8. Air chamber, emergency relay valve,
air reservoir and lines