scope:

Introduction

Electro-mechanical searchlight and banner repeating signals are fitted with a single permanently illuminated lamp, and the required aspect is selected by the mechanical rotation of a filter or mask. One or more outputs from the Interlocking drive the motor which controls the position of the filter or mask; if all outputs are de-energised the filter or mask returns to the most restrictive aspect. Because of the risk of a mechanical fault resulting in the display of an incorrect aspect, proving contacts are provided which allow the Interlocking to detect the displayed aspect, which can then be taken into account in aspect sequencing calculations and in the control of the indications on the Signalman's Panel. Searchlight signals are covered in Sections 2 & 3, and banner repeating signals in Sections 4 & 5.

Fibre-optic banner repeating signals have no moving parts and the standard type employs three lamps, two for the "on" aspect and one for the "off" aspect. Therefore controls and proving are somewhat different from that of electro-mechanically operated banner repeating signals, and are described in Sections 6 & 7. Section 8 covers splitting banner signals but only in fibre-optic form.