I thought I would contribute a page on the subject of signalling in the hope I can make the subject clearer. I will try to keep the subject general, as, if you look hard enough there is a prototype for almost everything!

While not wishing to complicate things too much; it is necessary to introduce some terminology that I will be using.

This will mainly deal with semaphore signals; there are two types the STOP signal and the DISTANT signal.

The STOP signal is a signal that can display a red aspect (a shunting signal is also a stop signal).

The DISTANT signal advises a driver of the state of the line ahead and if it is showing a yellow (CAUTION) aspect it tells him that the next stop signal will be red (at DANGER) and to proceed cautiously ready to stop. If it is showing green (CLEAR) then the next stop signal will also be clear.

Semaphore signals are horizontal when showing danger or caution and are either raised or lowered by about 45 degrees to show a proceed (CLEAR) aspect.

Not surprisingly, they are known as Upper Quadrant or Lower Quadrant signals respectively.

 

The signals are normally worked from a lever frame located in a building but sometimes out in the open.

The levers have two positions, (NORMAL) and (REVERSE).

When standing looking at the frame, levers away from you are NORMAL and those towards you are REVERSE.

When the levers are NORMAL the signals will be at DANGER or CAUTION points will be set as shown on the signal box diagram.

A signal showing STOP or CAUTION is known as being "ON" , when it is cleared it is known as being "OFF".

Up till the passing of the Light Railway act of 1896, unless the line was built as a tramway (like the Glyn Valley Tramway) then full signalling would have been provided unless the line was operated using one engine in steam only like the Talyllyn Railway.

The Talyllyn though,when it opened,had a couple of level crossings and these had to be provided with signals; bridges were eventually built and the signals dispensed with.

The 1896 act only required signals where trains were to cross at a loop on a single line. If the stop signalcould be seen for more than a quarter of a mile then a distant signal was not provided.

Signalling installations, once provided, did not need to be altered if standards were improved but if major work was carried out then that work had to be to the current standard in force. This is why the signalling on the Ffestniog Railway was of different standards. Tan-y-bwlch was signalled earlier than Blaenau Ffestiniog which was almost main line in its appearance.

The installation at Tan-y-bwlch on the Ffestiniog is a good example of early signalling. The two armed signal shown in many old photos and now replicated in a slightly shortened form actually controlled admittance to the station area rather than might be imagined departure from it. It's position is a throwback to even earlier days of signalling on the standard gauge railways. The signal was controlled by a mechanism at the base of the post and not from a lever frame hence its position at the centre of the station. Drivers would stop at the points at the entrance of the loop if the signal was at danger, entering the station when  it was cleared. Departure from the station was authorised by the Station Master after giving the driver the staff (or token) for the next section of line.

 

The next development was the provision fully interlocked installations worked from a lever frame. These installations were no different to those carried out on standard gauge railways in the 1880 and early 1890's. The North Wales Narrow Gauge Railways was one and in Ireland there were several, the Tralee and Dingle being one I have details of. The work was usually carried out by Signalling Contractors using their standard products.

As mentioned above this act simplified the provision of signalling due to the low train speeds permitted and was usually limited to crossing places on single lines although the Inspecting Officer could insist on its provision if he thought it necessary.

 

(to be continued.........)