U-Boat fan Wrote:
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> With the news about Illinois Ry Museum getting a
> CB&Q U28B (HERE), I got some questions...
>
> On the nose lights, do both the white and red
> lights oscillate? Or only the white one?

Both.

> Was the red light most likely related to train
> brakes? Perhaps to indicate train is in
> emergency?

Generally speaking, yes.

The specific light in question is a Mars Signal Light, which makes a figure 8 in a horizontal plane. Either the white beam or the red beam can be illuminated at any given time, but not both. There is a four-way control switch on the control stand marked OFF, DIM, FULL and RED; DIM and FULL are for the white bulb, RED is for the red bulb. In addition, there is a three-way switch marked INCH, OFF and RUN that controls the motor that operates the light when the white beam is on. The white beam or the red heam was manually turned on or off in accordance with what was prescribed in the Book of Rules. A circuit breaker (or on early units such as F units, a 30 amp fuse) provided electrical power for the signal light. Only the leading unit of the consist needed to have the circuit breaker in the "on" position. Some railroads used signal lights with only a white beam.

If the railroad used signal lights with a red beam, a control box was provided that included a pipe connected to the air brake train line and a pressure switch. If the circuit breaker was "on" and the pressure in the air brake train line fell below approximately 30 p.s.i., the pressure switch would drop out and the red beam would automatically illuminate (if the white beam was on at the time, it would automatically extinguish regardless of the position of the control switch in the cab) along with a RED SIG LIGHT indicator in the cab. Movements encountering a train on an adjacent track that was displaying the red beam were required to immediately reduce their speed and be prepared to stop short of the track ahead being fouled (for example, by derailed cars).

Some railroads permitted the oscillating red beam to be displayed as a marker light on the trailing end of the rear unit of a light engine in the same manner as it was used by some railroads on the rear car of a passenger train, but that's a different scenario.