The Oscitrol Light appeared on locomotives in the early to mid 70s. They were gone by the arrival of the 80s. The light was manufactured by the Mercor Corporation and was distributed by Power Parts Company. US Pat. 3,908,179 illustrates this light unit.
It is interesting to note that this was the last invention of Arthur C. Heehler (a co- inventor of this light died around 1975). Heehler was the inventor of the 20585 Gyralite while at Pyle-National, as well as most Gyralites. He was also a mechanical specialist at the Mars Signal Light Company prior to Pyle-National.
The PPC-11200 Oscitrol Light (PPC - Power Parts Company) was a column of 3 lights arranged to be mounted vertically to the locomotive. The 2 uppermost lamps were clear (white), while the lower was red. The 2 upper lights were aimed downward to the right and left of the projected centerline of the unit by 3 degrees, while the lower red light was aimed "straight ahead" along the unit's projected centerline. The red light would flash upon an emergency braking condition (low air pressure). The 2 upper lights had a flash rate of 50 right-left flashes per minute. The lower red light also produced 50 flashes per minute if activated. These lights "flashed" by going from dim to bright. The lights on this unit were also available individually as PPC-11300 Oscitrol Lights. In this way, the railroad could have the option of placement and configuration of these lights on the locomotive.
The Oscitrol Light was promoted as having the advantage of total solid state circuitry with no moving parts. It was most likely developed to replace the mechanical warning lights but failed to do so. Many railroads tried the light out but later removed it.
The Santa Fe had 10 SD40-2s equipped with the Oscitrol triple light fixture (PPC- 11200). It had the two clear lights on the top and the red light on the bottom. The light was mounted in the short hood. These units were installed in Santa Fe 5058 - 5070, renumbered BNSF 6717 - 6729. I am sure these lights were removed long before the BNSF merger.
Speaking of the Oscitrol, I know that they are not glamorous, but I have to admit that they were a fairly good idea that was indifferently executed (IMHO). I would have loved to have gotten hold of a new one back when I was into the electrical stuff by default. I remember them on the IC/ICG, and they weren't nearly as eye-catching as the oscillating lamps, but they sure did let you know when the air was dumped.
SP Oscitrol Light:
Power Parts Co. provided Oscitrol Light units to GE for application on SP locomotives. These units had a modified plate that did not include a red light. Two PPC-11300 units were mounted on this modified plate.
These Oscitrol Lights were installed on the GE SP B36-7s: 7754-7769 (SN 43791- 43806) in 1984. These lights were removed before the 1996 UP merger, being replaced with solid state amber bubble lights. After the merger, the numbers UP assigned to these locomotives were 385-399. However, 386, 388, 391-393, 397-399, - were retired on May 17, 1997, before receiving the UP numbers. It is interesting to note that this order of B36-7s was one of the first new unit orders delivered without classification lights. These Oscitrol Lights were applied to both ends of the B36-7 SP locomotives. A switch in the cab (on the engine control panel) switched operator controls between the front set of lights and the rear set, depending on what direction the locomotive was heading.
Individually available PPC-11300 Oscitrol Lights are now sold by New Vision Manufacturing for ditch lights. These are used on the BNSF SD70Is - and seem to be the ditch light fixture that EMD uses.
I was reading my SPSF Roster book over the past few days and noted that the SP was applying the Oscitrol light to a lot of locomotives during the mid 1980s. It seems they had a short lived program to replace the Gyralite with the Oscitrol. After a few units were completed they switched to installing the yellow bubble lights like their future merger partner's specifications. The book has a lot of pictures of rebuilt EMD units with the Oscitrol applied.
Another photo in the same book shows the rear Oscitrol of the SP B36-7s. The same fixture is used (including louvers!) The difference is the light bulb holders are rotated so the left bulb aims left and the right bulb aims right. Probably easier and cheaper to leave the louvers on even though they serve no purpose on the rear end of the unit. The units were installed horizontally so the top became the left. The former top light was rotated 90 degrees clockwise and the bottom light was rotated 90 degrees to the right as well. The holder on both would swing out to the left.