(2) A pneumatic throttle is equivalent to a pressure regulating valve. Responding to the
pressure established by the throttle, a pneumatic actuator determines the fuel setting of the governor. A
pneumatic throttle has auxiliary contacts similar to those of the electric throttle for sequence and
interlocking features. In multiple-unit operations, an air line furnishing air pressure equal to the control
reservoir pressure is required between the units.
b. Reverse lever. The reverse lever controls magnet valves in the reverser, which turn the drum
to change the connections of the traction motor fields. This lever must not be moved when the
locomotive is moving because circuits may be shorted. If the locomotive is unattended, the lever should
be taken off of the control stand in order to interlock the controls in an inoperative position. A seven-
position reverse lever, sometimes called a controller, is used on many manually controlled transition-
type locomotives, instead of a transition lever.
c. Transition lever. Ordinarily, a transition lever is provided on locomotives having manually
controlled transition. It may also be installed on locomotives having automatic transition in order to
control circuits during multiple-unit operation with locomotives having manual transition. A braking
position, for dynamic braking, is sometimes provided. Because of the definite relationship between
current and speed, the proper step of transition is usually indicated on the dial of the load ammeter or
speedometer.
d. Automatic brake valve handle. The automatic brake valve controls the operation of brakes
on the locomotive and on the cars when they are properly connected. The independent brake valve
controls the operation of brakes on the locomotive only.
e. Transition forestalling switch. A transition forestalling switch on the control panel is used to
prevent undesired forward transition on automatic equipment. Backward transition is determined by the
operation of a backward transition relay, or by reducing the throttle to the idle position.
f. Control switch. A switch, usually called the control switch, connects the control circuits to
their source of power. All controls except those for the locomotive lights and, in some models, the
engine starting circuit are normally fed through this switch, or through interlocks whose setting is
dependent on this switch. It is, therefore, equivalent to a master switch for locomotive controls on both
the leading locomotive and on any trailing locomotive to which the controls are connected in multiple.
43
Previous Page
