The dynamic braking system is independent of the airbrake system, which may also be used on
the train. Military diesel-electric locomotives are not equipped with dynamic braking; they use only the
PNEUMATIC CONTROL SWITCH
When emergency brakes are applied or under similar conditions, engine power is reduced by a
pneumatic control switch that opens when the brake pipe pressure is reduced. The opening of the switch
stops the engine, stops the fuel pump, and turns on indicating lights. When the throttle is returned to idle
and the brake pipe pressure is restored, the switch resets itself.
Most of the electrical equipment on the locomotive is mounted in a centrally located cabinet.
The operator's control station is located in the cab, shown as item 8 in figure 1.1. Locomotive
movement is directed by a series of controls: throttle, reverse and transition levers, automatic and
independent brake valve handle, transition forestalling switch, and control switch.
a. Throttle lever. The throttle controls the speed of the diesel engine and, consequently, the
power delivered to the traction motors. If a throttle functions through an electropneumatic or electro-
hydraulic governor, it is called an electric throttle and must be connected electrically to the governor;
one that functions through the air system is called a pneumatic throttle and must set the governor through
a pneumatic actuator. Some locomotives have a mechanical linkage between the throttle and governor.
(1) A typical electric throttle has seven or eight running positions in addition to "stop" and
"idle." As the throttle lever is moved through its operating range, various electrical connections are
made between the low-voltage control lines and the solenoids in the governor. Fingers, making sliding
contact with segments on a rotating drum or cylinder in the throttle, determine the fuel setting of the
governor. The throttle is also interlocked mechanically with the reverser and with the transition lever if
transition is controlled manually. These features ensure the opening of the main power switches when
necessary during various stopping and reversing operations.