I'm posting a photo by Michael Christy from his Railimages album, showing lower quadrant semaphores on CORP in Oregon. I know that Gil (signalguy) and LEW know all about the different types of signals used by the RR's in the past many years. Gil, and LEW, can you explain the differences between upper quadrant and lower quadrant semaphores, and perhaps shed some light on those B&O light signals with so many different aspects? Thanks in advance. Peirce, I know you will help out on this too.
fitz as you are aware I'm a Signal Engineer here in australia and we do follow similar priciples of signalling although we follow the UK system more closely. The difference between lower quadrant and upper quadrant are basically self explanatory. Lower quadrant when clear , clear to the lower quadrant as seen in the picture above where as upper quadrant raise to between 45 and 90 degrees.
The semaphore shown is a Union Switch & Signal (US&S) lower quadrant type and can display three aspects. With both arms down at the 45 degree position as shown it displays Clear. With the bottom arm at 90 degrees (horizontal) and the top arm at 45 degrees |\ |_ it displays approach. With both arms at the 90 degree position the signal displays stop. |-- |-- On the upper quadrant semaphore the arm is capable of displaying three aspects. With the arm in the vertical position (|) it displays a clear aspect. When the arm is at 45 degrees (/)it displays an approach aspect and when the arm is horizontal (--) it displays a stop aspect. The upper quadrant type semaphore usually has only one arm while the lower quadrant usually has two arms.
Here it is visually, in this first pic the semaphore on the left is upper quadrant, i.e. it raises to show clear, the distant arm below it is at caution: In this second pic the semaphore is lower quadrant, i.e. the arm drops to show clear. (The train in shot here is backing up, hence the odd situation of signal and train) There's lots of different meanings between US and UK (and presumably Australian) ways of using them and their meanings though..
Martyn You reminded me that one railroad, as far as I know, in the US had upper quadrant semaphores where the arms were on the track side rather than the field side. This railroad was the New York, New Haven & Hartford. In the electric zone between New Haven and New York their three arm home signals had two arms on the catenary structure and a dwarf semaphore on the ground as there was not room for all three on the structure. Perhaps Peirce might have a photo of one. \| Yellow _| Red -| Red
Mmm, those New Haven ones sound interesting. All the various UK companies I can think of had them pointing to the left (which would be 'field side' over here as L/H running is normal - although there are places where the signal was located on the wrong side of the line to aid sighting, so those would end up pointing to the track.)
It is normal in the US for the semaphore signals to be mounted to the right of the track (right hand running) and the blades of both upper and lower quadrant to the field side. The FRA requirements previously required signals to be located to the right of or over the track governed. If a railroad wanted to install a signal to the left of the track governed it required a special application and FRA approval. This requirement was changed in the 80s and now you see many new installations on single track of back to back signals where one signal is to the right and the opposing signal is to the left. This eliminated the need to bury cable from the relay case to the signal on the opposite side of the track. It also saved a signal foundation and mast. On double track with reverse running on both tracks signals are installed back to back on both sides of the tracks and this eliminated many signal bridges.
Here's an example of one sited 'wrong side', the cleared semaphore in the background is for the train in the shot which has just passed it, that one is mounted not just to the right of the line, but to the right of the (directional) pair of lines, a track away from the one it applies to. Not a common arrangement, but it does happen when you get a sharp curve with limited foward view like here. The signal on the right of the shot is more conventionally on the left of it's track, but that's a 15mph goods siding, not the 55mph main line.
I'm bringing this thread back to life in hopes of some discussion about the purpose of the signals in different areas of the country. LEW educated my in the use of signals on the NY Central for speed control, but they have other purposes in other locations. Gil mentioned that lower quadrant semaphores have only two aspects, and would be illegal in some other places. How about it guys?
It is a one arm lower quadrant semaphore that can display a Green (Clear) into a Red (Stop)signal. There has to be a Yellow (Approach) between the Green and Red. A two arm lower quadrant semaphore has the Home arm on the top and the Distant arm on the bottom. The Home arm is clear when the next block is clear and the Distant arm is clear when both the next block and the second block are clear. [ 12. May 2004, 03:55: Message edited by: signalguy ]
Thanks, Gil. I was saving this shot to restart the thread again, but it's too good to hold. Photo by Ted Curphey (funnelfan) of the SP&S 700 at St. Regis, Montana, splitting the blades. Can you guys tell us what the blades are saying? Thanks.
Gil's explanation of the 'Home' and 'Distant' arms holds true for the UK shots I posted as well, the signal in that format is basically the equivalent of a 3 aspect colour light (red/yellow/green), in Gil's pic at the top it is showing the next two blocks are clear, equivalent to green, on my shot below it the signal is showing the equivalent to yellow, with the second block occupied (or more likely in this case the route not set, as there is a junction beyond the next block). The MRL (ex NP?) signals have what amounts to a 3 aspect semaphore, with 45deg equivalent to yellow and vertical as green.
The signal on the left is clear for the train but is about to drop to Stop (horizontal) as the train passes it. As the train proceeds through the blocks the signal will first change to Yellow (45 degrees) and then to Clear (vertical). The right hand signal (opposing) is at Stop (horizontal) but as soon as the last car of the train is clear of the block it will return to clear (vertical) unless there is a following train.
Gil .. I remember when Southern Pacific still operated over the Siskiyou line before it was leased to RailTex (C.O.R.P.) and I recall seeing semaphore signals on the California side of the summit indicating an oncoming train with a blade at 90 degrees, while the blade for the train in the block was hanging straight down. Is this one of the discrepancies that you were telling me about?
Bill - I was talking about one train following another and with the single arm signals he could receive a Green (Clear) aspect into a Stop (Red) aspect. In the instance you saw with a train coming the opposing signal was at Stop as the block that it governed was occupied. The arm for the train that was coming should have been at 45 degrees as it can not be vertical as it only has two positions.
I will try to do some B&O aspects later today. Here is a site with B&O signal aspects. http://broadway.pennsyrr.com/Rail/Signal/aspects_us_bo.html [ 13. May 2004, 03:11: Message edited by: signalguy ]
