I've plenty of photos / films of E or F-unit engines with the main lower headlight on and the Mars or other oscillating upper headlight off. I can't imagine that the Mars light would be moving hour after hour while it's turned off, that would waste a lot of electricity. Common sense would say the light could be turned off as could the moving parts that made it oscillate.
Mel,
As far as I know, the GS-4s, like most SP diesels of that era had Mars lights. The pattern of movement between the two brands of light, Mars vs. Pyle looked different and the Pyle looked more like it could be aimed in a specific direction than the Mars. I seem to remember a GE, probably a U33C with a Pyle Gyralight that although illuminated, was not gyrating. This was back in the late 1970s. Maybe it was an option?
IIRC I read about D&RGW using theirs to look to the side to see better on curves, which they had a lot of. They could stop the light in a position that was to one side or the other.
Rio Grande. The Action Road - Focus 1977-1983
Probably an option the purchasing railroad could specify:
http://www.trainweb.org/gyra/specs/c100.htm
Note that the second control switch, the WR 1000, has a jog function so the lamp can be aimed in a desired angle.
As you can see here, the two clear and one red lamps are mounted to the same "swash plate". Certainly would be simple to have a selector switch to stop or jog the motor. If brakepipe pressure saw an emergency application the red oscillating light would override and come on until reset.
Aerotrain_nacelle by Edmund, on Flickr
The 350 W. PAR-56 lamps are 7" diameter and the red lamp is 8-3/8" diameter.
I have a Gyralight. There is only two wires and the lamp is in series with the motor relay. If the lamp burns out the motor will not run.
Cheers, Ed
A while back I asked a question about mars & gyralights and I appreciate all those who contributed to the topic. I now have a supplimental question about the same:
Was the mechanical portion of the headlight something that could be engaged and disengaged? Or was it always oscillating - even when turned off?
I was just curious if a mars or gyralight could ever be used as a stationary "constant" headlight? Thanks ahead of time for your input.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.