Any position of the pointer in the red portion of the scale indicates an overload which MUST be reduced immediately to prevent possible damage to the motors and the resistor assembly. On the other type, Fig. 4-0, the red zone at the high current end of the scale represents a heavy overload. Operation in this zone is normally used for starting and accelerating the train. A train of the proper tonnage should not require more than approximately 4 minutes operation in this zone. Yellow zone operation is permissible for a consecutively or accumulated time not to, exceed 90 minutes.
Continuous operation is permissible in the white zone.
As the speed of the locomotive increases or decreases, the selector handle should be moved to the corresponding position indicated by the pointer. On locomotives equipped with automatic transition, the inner scale is omitted leaving only the miles per hour scale. Two standard air gauges are furnished, one indicating brake cylinder and brake pipe air pressure while the other main reservoir and equalizing air pressure. This instrument should indicate a battery voltage of 64 when the engine is shut down and the battery switch closed. A lower reading than this would indicate that the battery is not fully charged or has faulty cells.