TM 9-2330-294-14
emergency air line, t h e service brakes are
2-4. Brake Release Controls
automatically applied by captive air from the
reservoirs, Pushing in the service brake release
a. Service Brake Release Control Knob. T h e
control knob isolates the semitrailer emergency air
service brake release control knob is located on the
line and uses stored air to pressurize the emergency
frame left side member forward of the air suspension
port of the emergency relay valve and thus releases
controls and is identified by an identification plate.
the service brakes, This knob is automatically reset
When the semitrailer becomes detached from the
to the "out" position when the air pressure is
towing vehicle or when a severe air leak occurs in the
restored to the emergency air line.