This being the UK group, re-arrange the above as follows: Upper quadrant home signals have the arm at 9:00 for stop and 10:30 for proceed. Lower quadrant home signals 9:00 for stop and 7:00 for proceed. For distant signals stop is replaced by caution.
Wioth the exception of a couple of tiny experiments 3 position semaphores were not used in the UK, as someone else mentioned, by the time we got around to 3 aspect signalling colour lights were chosen for it.
For a model dated prior to 1925 only lower quadrant signals will be needed, upper quadrant came in post grouping in all areas except the GWR which retained lower quadrant.
Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.
Note that 3 position semaphores were not used in the UK. In USA practice the 3 position semaphore was used interchangeably with
3 aspect colour lights, the normal rest position could be any of the 3 positions depending on the particular signal. Interlocking signals, ie those protecting points, would be normally at stop. Automatic block signals would be normally at proceed unless the next signal is an interlocking signal in which case it would normally be caution. (Interlocking signals commonly had 3 arms each but that's another story). Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.
Semaphore signals are an excellent application for memory wire. See
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and click on links in the left-hand column for working examples.
I believe only 2-position semaphore signals were used in Britain, at least as of the mid-20th century. Distant or caution signals are yellow with a notched end and black chevron, and green/yellow spectacles; home or stop signals are red with a square end and white band, and green/red spectacles. An upper quadrant signal would normally rest at danger, and would fall there if the actuating cable broke. It would be "pulled off" to the clear position. A lower quadrant signal requires counterweights to return to the "fail safe" danger position. Lower quadrant signals were mainly used on the GWR/BR(WR).
I'm sure other experts here can add to my skimpy knowledge, or you can always Google.
Many methods were used in the very early days, flags, balls, discs lamps etc. After a short time the semaphore arm came into common use.
Initially most arms "disappeared" into the post when the line was clear (so called slotted signals) and only showed as a stop indication. This was found to be unsatisfactory after a number of collisions when the arms froze into the slot (notably at Abbots Ripton on the Great Northern Railway in 1876). This also soon resulted in signals being normally "stop" and only pulled off to allow a train to pass.
Then, as speeds increased, there came a need to have additional warnings of a "stop" indication and the "distant" signal came into use. These were distinguished by a fishtail notch cut into the end and being coloured yellow (notch first used by LBSCR in 1872, universal by
1877)(yellow took longer to become universal).
Thus the semaphore arm came into use. This was always horizontal for stop (or caution in the case of distant signals) and 45 degree angle for proceed, either lower quadrant or upper quadrant. The one major exception was the Great Northern which used centre hinged semaphores which showed horizontal stop and vertical proceed.
Lights were also shown, initially with white as "go" - in 1893 rules were changed to make this green and conversion took until the early part of the 20th century. The distance signals originally also red for "caution" - this was changed to yellow from 1917 (completed by 1930).
All semaphores should default to the "stop" aspect if the wire breaks - this is easy with upper quadrant but needs counter balances for lower quadrants. [cannot find in the book - but recall the Great Way Round (GWR) was the main user of lower quadrant]
3-position semaphores were extremely rare. There was an experimental installation at Paddington in the 1930s but this didn't last very long.
[They were common in the US but not the UK, and US signalling practice was completely different and this is a UK newsgroup]
A stop (red) signal is absolute. Stop or go.
There is a distant (yellow) at a decent stopping distance before the stop. This indicates caution or go.
It is backed up by an AWS (Automatic Warning System) that puts the brakes on if the driver does not operate them. An emergency stop instead of the driver's controlled stop at the red.
The default aspect is the horizontal (stop/red or caution/yellow).
The track length between two stop signals [outside station limits] is known as a block.
Entry to a block is controlled by a stop signal, and only one train is permitted in a block at a time. The distant signal is actually within the previous block.
Most modellers don't have distant signals because they would be off the layout - a mile or more before the stop. Apart from a few special cases where a distant for the next stop is mounted on the same post as the current stop, but this is less common.
No. The normal aspect is "stop". The signals are also constructed so that if the mechanism fails they show a stop indication.
Semaphore signals are operated by a cable from the signal box. When the lever is pulled, the cable raises a weight on a lever at the base of the post. The signal arm is actually operated by a rod from this lever. When the lever is released [or the cable breaks], the weight makes the lever drop and the rod returns the signal to danger.
If the rod breaks, the signal arm is balanced so it will fall to the horizontal - even lower quadrant signals [which are pivoted between the arm and the spectacle plate which is heavier than the arm].
The signalman returned them to stop after the train had passed.
He cannot set a route, etc unless everything is at stop while he does it. The levers for the points and signals are interlocked and prevent this. They've also got to be set in the right order.
In a yard the rules can be relaxed. Later ground signals were "independent", ie they were separate from the points and operated from an interlocked lever frame - not necessarily in the signal box. The shunter could do it from a ground frame in the yard. Earlier ground signals were operated from the turnout and were just indications of which route was set. Some of these lasted very late, even when you would expect them to have been replaced.
If you go to the North York Moors Railway one of the features that screams North Eastern Railway, are the slotted post signals where the arm pivots inside the post not outside.
While these lasted longest there, other lines also had them so if you are modelling eg the GWR circa 1900 you could have the occasional slotted post signal as well as the more usual GWR lower quadrant.
Thanks heaps for your info! It is brilliant to have such in-depth knowledge at one's fingertips - no idea how I would've gotten this info pre-net!
Ok, so if I was happy to create a "standardised" semaphore (illuminated if possible) system on my early 20th C layout, what would be an acceptable style? Any pics available?
Also, as it has been many years since I did any of this, and I was a kid, I don't know what terms like "distance" implies.
Early warning signal placed some distance from 'home' signal and sometimes indicating that next signal is at 'stop'. Distant signal can be ignored by driver if he likes but home signal has to be obeyed at all times.
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