Lower Quadrant Semaphores

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Lower Quadrant Semaphores
Posted by Texaswestern on Sunday, November 24, 2019 9:20 AM

The Southern Pacific and Union Pacific railroads used Lower Quadrant semaphores.  Did other railroads in the United States, besides the Texas & New Orleans, use them as well?

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Posted by timz on Tuesday, November 26, 2019 12:17 PM

Think the first upper-quadrant semaphores in the US appeared about 1907, on PRR; before that, some RRs used Hall disc signals, but more used lower-quadrant semaphores. PRR used lower-quadrant, but replaced them all -- dunno how many other RRs did the same.

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Posted by wjstix on Tuesday, November 26, 2019 12:47 PM

Of course, many railroads used upper-quadrant semaphores for block or interlocking signalling, but used lower quadrant for train order signals like at stations or towers. The blade extended meant 'stop for orders', the blade all the way down meant 'no orders', and the blade in between those two meant orders needed to be picked up on the fly.

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Posted by rcdrye on Tuesday, November 26, 2019 2:06 PM

Boston & Maine used them in may places, eventually replacing them with searchlight signals.  Chicago & North Western used them along with Hall "Banjo" signals, replacing the Hall signals with more blades before replacing the semaphores with horizontal multi-light heads.  A few even showed up on interurbans, notably the Washington Baltimore & Annapolis.

Where used for block signalling they were almost always set up with dual blades, the lower blade repeating the aspect of the top blade at the next signal.  This allowed three indications to be presented.

Color light         Semaphore

Red                   both blades horizontal

Amber               top blade at 45, bottom horizontal

Green                both blades at 45

Automatic signals of this type were rarely configured for 90 degree operation, though lower quadrant train order signals were.

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Posted by M636C on Tuesday, November 26, 2019 9:13 PM

While not completely relevant, in Australia lower quadrant signals were generally manually operated by wire while upper quadrant signals were invariably motor operated. All automatic semaphores were upper quadrant.

What colour lights were used with USA upper quadrant signals?

Here they were horizontal = red, 45 deg. = amber, vertical = green.

We had some "distant" signals that had an upper fixed green light without a blade and the lower blade could show red amber or green depending on the aspect of the following signal.

There were some double blade signals as well which could act either as a "home" or a "distant"

I'm sitting at the top of the great dividing range waiting for the twice weekly passenger train to Griffith, a two car railcar. Just to my right is the site of a former distant semaphore which acted for the home signal at Cullerin, the highest station between Sydney and Melbourne. I guess it has been gone for ten years now.


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Posted by rcdrye on Wednesday, November 27, 2019 6:48 AM

What colour lights were used with USA upper quadrant signals? Here they were horizontal = red, 45 deg. = amber, vertical = green.

Same as the U.S.

Most railroads using lower quadrant semaphores used pointed blades for the "home" (top) blade and a notched blade for the distant (bottom) blade.  For interlockings all blades got a square end.  There were, of course, many exceptions to this.


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