Railway Signs and Signals of Great Britain

In 1893, 'calling-on distant' signals (or 'station distant' signals) were introduced on the North London Railway. They were similar in appearance to ordinary calling-on signals but their arms were fishtailed, and they were placed below a main distant arm [4.21]. When cleared, the calling-on distant indicated that the home signal ahead was 'off' but the starting signal was 'on' [4.22]. In accordance with North London Railway practice, rings were fitted to the arms of signals applying to the 'No.1' lines [4.23 & 4.24].

[4.21] Calling-on Distant Signal ('on') (NLR).	[4.22] Calling-on Distant Signal ('off') (NLR).


[4.23] Ringed Calling-on Distant Signal ('on') (NLR).	[4.24] Ringed Calling-on Distant Signal ('off') (NLR).

A 'shunt-ahead' signal may be provided at a main stop signal that controls the entrance to the section ahead. When cleared, it authorises a train to pass the main signal for shunting purposes only, so that it may then set back through some trailing points. There were various designs of shunt-ahead signal [4.25 - 4.30].

[4.25] Shunt-ahead Signal ('on') (NBR).	[4.26] Shunt-ahead Signal ('off') (NBR).


[4.27] Shunt-ahead Signal ('on') (GWR).	[4.28] Shunt-ahead Signal ('off') (GWR).

[4.29] Calling-on or Shunt-ahead Signal ('on') (S&DJR).	[4.30] Calling-on or Shunt-ahead Signal ('off') (S&DJR).

A 'warning' signal, when cleared, authorises the driver to proceed to the next stop signal. The driver must understand that the line is clear as far as the next stop signal only, but might be obstructed immediately beyond it. The speed of the train must be regulated accordingly. Where provided, a warning signal was usually placed at a main stop signal that controlled the entrance to the section ahead.

Warning signals were uncommon at one time, but the LB&SCR had some in the London District, working in conjunction with Sykes Lock and Block [4.31 & 4.32].

[4.31] Warning Signal ('on') (LB&SCR).	[4.32] Warning Signal ('off') (LB&SCR).

The Great Central Railway also had a few warning signals, working in connection with Evans Lock and Block. These comprised a small centrally-pivoted semaphore arm with a distinctive sloping end [4.33 & 4.34].

[4.33] Warning Signal ('on') (GCR).	[4.34] Warning Signal ('off') (GCR).

Where the Great Western Railway provided banner type main signals (see [2.72 & 2.73]) and a calling-on signal was required, it took the form of a miniature banner endorsed "CO" on the arm [4.35 & 4.36].

[4.35] Banner Type Calling-on Signal ('on') (GWR).	[4.36] Banner Type Calling-on Signal ('off') (GWR).

In 1920, the GWR's Ealing & Shepherd's Bush Railway was resignalled with three-position semaphore signals working in the upper quadrant (see Section 2). Where calling-on signals were required, they comprised two-position semaphore signals (also working in the upper quadrant) endorsed "CO" on the arm, with one letter on either side of the white stripe [4.37 & 4.38].

[4.37] Calling-on Signal ('on') (GWR).	[4.38] Calling-on Signal ('off') (GWR).

Where a main signal in the form of a large disc (see [2.90 & 2.91]) required an associated calling-on signal, the latter would be a normal-sized disc endorsed "CO" [4.39 & 4.40].

[4.39] Disc Type Calling-on Signal ('on') (GWR).	[4.40] Disc Type Calling-on Signal ('off') (GWR).

The Ministry of Transport 'Requirements' of 1925 had stipulated that calling-on and shunt-ahead signals (warning signals were not mentioned) should display a white light in the 'on' position. It therefore followed that the colour of the signal arm should also be white. Around 1925, a subsidiary signal comprising a small white arm with two horizontal red stripes was installed on the LNER (at Cambridge) [4.41]. To distinguish more clearly the functions of the various types of subsidiary signal, around 1925, distinguishing letters "C", "S" or "W" began to be exhibited alongside the lamp when the signal arm was 'off' [4.42 - 4.47]. The letter was hidden behind the arm when 'on'.

[4.41] Subsidiary Signal ('on').

[4.42] Lower Quadrant Calling-on Signal ('off').	[4.43] Upper Quadrant Calling-on Signal ('off').


[4.44] Lower Quadrant Shunt-ahead Signal ('off').	[4.45] Upper Quadrant Shunt-ahead Signal ('off').

[4.46] Lower Quadrant Warning Signal ('off').	[4.47] Upper Quadrant Warning Signal ('off').

Section 4: Subsidiary Signals

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