Hello people, would anyone be able to tell me how a 2 aspect search light signal (red on top with green underneath) used at the enterance of a passing loop on an western RR in the early 1950’s, would show if the main line is clear for a train to go through? I know that a 2 aspect search light signal showing red on top with green underneath means that the passing loop (or siding if you like) is clear for a train to pull into and that the railroad point is set to that siding, but how does the 2 aspect search light signal show if the point is not set to the passing loop and that the main line is clear for the train to enter? does the top aspect have both a green and red light in it, because to me it looks like it only has one light in it which is red coloured?
A two-head signal displays the condition of two different routes. Thus, if the main (most usually used, through or fastest) route is clear for full speed running, the upper head will display green. If that route has automatic block signalling and there is a train not too far ahead, the same head will display yellow. If the turnout has been lined to the other route, the upper head will display red. Likewise, red will be displayed if there is a train that has not cleared the block protected by the ABS feature of the system.
The lower secondary route signal head will always display red if the turnout is set for the main route. When the turnout is lined for the secondary route, the signal may clear to green if the turnout can be taken at full speed and the route beyond is clear. If speed must be restricted, the secondary route may only clear to yellow.
The prototype single-lens searchlight signal has a single bulb. A spectacle between that bulb and the lens carries color plates of appropriate color (green, yellow,red) and a small motor positions the appropriate plate between the lamp and the lens - sort of a miniature semaphore signal completely hidden within the signal head.
Thanks for answering my question, by was this lens changing used in the early 1950’s too and how would the lens changing be modelled in HO scale as I would imagine that the lens diameter would be very small to fit in 3 LED lights, or would it be possible to do so?
The easiest way would be to use bi/tri-colored LED’s. The two-lead type will display different colors depending on the polarity of the input voltage. The red/green types will display 3 colors - red and green on DC, and yellow on AC current. Trying to model the actual mechanism of a searchlight signal is unnecessarily complicated. If they were bright enough, the prototype would use LEDs, I’m sure - no moving parts = lower maintenance costs.
Searchlight signals are still in use today, and have been since at least the Thirties…
The NYC had searchlight signals in service on the West Shore division in 1950. They were approach lighted, which meant they were normally dark. When one lit up you knew that a train had entered the block and would shortly be coming up from behind you if you were facing the signal.
Thanks guys! Also did those approach lighted search signals have the ability to change colour and were the used on western roads in the 1950’s too?
Sorry, but I forgot to mention before if anyone would know what the diameter on a search light lens would be? thanks!
First lets get some terms corrected(too much confusion). A ‘searchlight’ signal has one lamp, with a moveable vane between the lamp and the lens. They get all the colors from that single signal head. I assume this is what we are talking about. With a dual head signal, a RED over GREEN will usually be the indication for entering a divirging track at medium speed. A GREEN over RED is an indication for normal movement through the interlocking at track speed.
Approach lighting is used to save battery life, and can be used on searchlight signals. Approach light has been in use even before the 50’s. As far as the size of the lens, not sure. GRS and US&S both made these signals and maybe someone here has dimensions.
Jim Bernier
Another way to model the searchlight is with fiber optics, with whatever mechanism you need mounted under the layout.
While some railroads may have had a “take siding” indication, in Canada the signals were speed indicators. With 2 heads and 3 colours there are 9 combinations, although I don’t believe green over green was used.
With these signals, you can indicate how fast the train should go through the switch and what they should expect at the other end of the siding (or the next signal along the siding.)
Actually there’s another possibility…Lunar, a bluish white. In a situation where the rail joints in the siding aren’t bonded (for electrical continuity) the upper signal would show red and the lower lunar, indicting that the siding was to be entered at restricted speed in case there was rolling stock or an improperly lined switch in the sidng.
As a rule of thumb, the color of the signal tells you how fast to go and it’s location tells you what track you’re going to.
Thanks guys for all your help, you have given me information which has DEFINITELY cleared up my understanding on how these signals work! Thanks!!
I’m not sure if you can use this, but here goes…
http://www.trains.com/community/forum/topic.asp?TOPIC_ID=51410
The link does work grande man, thanks! Also, I actualy came across that page before, but I thank you for reading my posts and providing that link for me! I see that you model a fictional route of the D&RGW RR in the 1960’s as I too have an interest to model the D&RGW RR but in the early 1950s, so just out of interest, would you know if the Santa Fe RR ran under traffic rights over La Veata pass in the early 50’s to Alamosa (about mid south Colo) where the narrow gauge D&RGW conected with the strd gauge?