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Section 4: Subsidiary Signals

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In the early colour light signalling schemes (e.g. the Great Western Railway's E&C Lines in 1927), calling-on signals comprised a small green light mounted below the main signal head. The light was normally extinguished, being lit to authorise a move past the main signal [4.49]. The LMS followed semaphore practice by displaying a small white light for location purposes when the calling-on signal was 'on' [4.50]. In practice, however, the white light was prone to being mistaken for a yellow 'proceed' light.

[4.49] Calling-on Signal ('off').
Area: Various   Usage: Medium   Status: Historical
[4.50] Calling-on Signal ('on').
Area: LMS   Usage: Medium   Status: Historical

In 1928, the Southern Railway introduced a new standard form of semaphore subsidiary signal, having a white arm with a red horizontal stripe across the centre. Initially, calling-on signals of this type carried no distinguishing letter [4.51 & 4.52] whereas shunt-ahead or warning signals carried a red distinguishing letter "S" or "W" fitted to the front of the arm [4.53 - 4.56].

[4.51] Calling-on Signal ('on').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.52] Calling-on Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.53] Shunt-ahead Signal ('on').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.54] Shunt-ahead Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.55] Warning Signal ('on').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.56] Warning Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical

A single subsidiary arm may function as either a shunt-ahead or a warning signal depending on the circumstances. In this instance, no letter was fitted on the arm (see [4.51]) but, when cleared, a letter "S" or "W" was displayed alongside in an indicator [4.57 & 4.58].

[4.57] Shunt-ahead Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.58] Warning Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical

The Southern Railway subsequently decided that its calling-on signals should be fitted with a red letter "C" on the arm [4.59 & 4.60].

[4.59] Calling-on Signal ('on').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.60] Calling-on Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical

A sub-committee of the Railway Clearing House recommended in 1928 and approved in 1929 that the standard form of subsidiary arm should be coloured white with two horizontal red stripes (see [4.42 - 4.48]). The Southern Railway conformed with this and from 1929 was installing subsidiary signals coloured accordingly, but still with a red distinguishing letter on the arm [4.61 - 4.66].

[4.61] Calling-on Signal ('on').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.62] Lower Quadrant Calling-on Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.63] Upper Quadrant Calling-on Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.64] Shunt-ahead Signal ('on').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.65] Lower Quadrant Shunt-ahead Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.66] Upper Quadrant Shunt-ahead Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical

From this time, warning signals on the Southern Railway had arms without a distinguishing letter "W" fitted [4.67]. When cleared, a "W" was displayed in an indicator alongside the arm [4.68 & 4.69].

[4.67] Warning Signal ('on').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.68] Lower Quadrant Warning Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical
[4.69] Upper Quadrant Warning Signal ('off').
Area: Southern Railway   Usage: Unknown   Status: Historical