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Section 4: Subsidiary Signals

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The sub-committee of the Railway Clearing House recommended in 1929 that subsidiary signals in colour light areas should no longer be in colour light form and that 'optical projector' or banner signals should be used instead. This was agreed to by the Ministry of Transport on 26 September 1929, as was the use of the white subsidiary semaphore arm (see [4.41 - 4.47]). The arms of the banner subsidiary signals were horizontally striped (similar to the semaphore type) and had a letter "C", "S" or "W", as appropriate, printed in red on the face of the signal [4.69 - 4.74].

[4.69] Banner Type Calling-on Signal ('on').
Area: LNER   Usage: Unknown   Status: Historical
[4.70] Banner Type Calling-on Signal ('off').
Area: LNER   Usage: Unknown   Status: Historical
[4.71] Banner Type Shunt-ahead Signal ('on').
Area: LNER   Usage: Unknown   Status: Historical
[4.72] Banner Type Shunt-ahead Signal ('off').
Area: LNER   Usage: Unknown   Status: Historical
[4.73] Banner Type Warning Signal ('on').
Area: LNER   Usage: Unknown   Status: Historical
[4.74] Banner Type Warning Signal ('off').
Area: LNER   Usage: Unknown   Status: Historical

On the LMS schemes where colour light signals were provided with marker lights (see [2.104]), a calling-on indication was given by the red marker light being extinguished and replaced by a small yellow light [4.75].

[4.75] Calling-on Indication.
Area: LMS   Usage: Medium   Status: Historical

In the Great Western Railway's early colour light signalling schemes (e.g. Cardiff, 1933), subsidiary signals took the form of an 'opal plate', normally extinguished. When illuminated, the indicator displayed an image of a semaphore arm in the 'off' position, along with the appropriate letter "C", "S" or "W" [4.76 - 4.78].

[4.76] Calling-on Signal ('off').
Area: GWR   Usage: Medium   Status: Historical
[4.77] Shunt-ahead Signal ('off').
Area: GWR   Usage: Medium   Status: Historical
[4.78] Warning Signal ('off').
Area: GWR   Usage: Medium   Status: Historical

When the Cheshire Lines Committee's Manchester Central terminus was resignalled with colour light signals in 1935, the calling-on signals took the form of a small yellow aspect, with a letter "C" below [4.79]. No indication was given when the calling-on signal was 'on'.

[4.79] Calling-on Signal ('off').
Area: CLC   Usage: Low   Status: Historical

Later colour light signalling schemes on the Great Western Railway (e.g. Bristol East, 1935) discontinued the use of 'opal plates' (see [4.76 - 4.78]) in favour of subsidiary signals comprising a small green aspect, normally extinguished. When cleared, a small green light was displayed together with the appropriate illuminated letter "C", "S" or "W" [4.80 - 4.82].

[4.80] Calling-on Signal ('off').
Area: GWR   Usage: Medium   Status: Historical
[4.81] Shunt-ahead Signal ('off').
Area: GWR   Usage: Medium   Status: Historical
[4.82] Warning Signal ('off').
Area: GWR   Usage: Medium   Status: Historical

The RCH sub-committee recommended in June 1934 that, for the sake of uniformity, subsidiary signals in colour light areas should be of the same form as the shunting signals (see Section 3) at the same location. If the signal controlled entry into the block section, a distinguishing letter "C" or "S" would be required. The sub-committee also proposed that warning acceptance at colour light signals be given not by a subsidiary signal but by the main aspect, possibly to be accompanied by a letter "W". These proposals were accepted by the Ministry of Transport on 11 March 1936. Accordingly, provision of striped banner signals (see [4.69 - 4.74]) was discontinued in future schemes.

Around 1937, the Southern Railway introduced a calling-on signal, for use in colour light areas, in the form of a disc with a plain red band superimposed on a black letter "C" [4.83 & 4.84]. These discs were illuminated at night.

[4.83] Disc Type Calling-on Signal ('on').
Area: Southern Railway   Usage: High   Status: Historical
[4.84] Disc Type Calling-on Signal ('off').
Area: Southern Railway   Usage: High   Status: Historical

In areas where position light shunting signals were used, subsidiary signals were of the normally-out position light type. When the subsidiary signal was cleared, the two white lights were accompanied by a distinguishing letter "C", "S" or "W" [4.85 - 4.87].

[4.85] Position Light Calling-on Signal ('off').
Area: All Areas   Usage: High   Status: Obsolescent
[4.86] Position Light Shunt-ahead Signal ('off').
Area: All Areas   Usage: Medium   Status: Historical
[4.87] Position Light Warning Signal ('off').
Area: All Areas   Usage: Medium   Status: Historical

The 'draw-ahead' signal was first mentioned in a 1937 supplement to the Rule Book. Like a shunting signal (see Section 3), a draw-ahead signal authorises the driver to proceed towards the next stop signal but not to pass any shunting signal that may be at 'danger'. A draw-ahead signal would never be provided at a signal that controlled the entrance to the section ahead. A draw-ahead signal in semaphore form will be cleared to the 'off' position without any distinguishing letter being displayed [4.88 & 4.89].

[4.88] Lower Quadrant Draw-ahead Signal ('off').
Area: All Areas   Usage: Unknown   Status: Historical
[4.89] Upper Quadrant Draw-ahead Signal ('off').
Area: All Areas   Usage: Unknown   Status: Historical

By 1969, it had ceased to be a requirement for the distinguishing letter "C" to be displayed at a position light type calling-on subsidiary signal (see [4.85]). From 1983, the distinguishing letters "C", "S" or "W" (see [4.85 - 4.87]) were removed from position light type subsidiary signals.