Power Signalling At Bristol
High Speed Passenger Running Line signals are the type SA searchlight, giving red and green aspects for the Stop signals and yellow and green aspects for the distant signals.
The integrity of the lamp filament is proved by a type H relay operating in series with the 12V 12W signal lamp, which is supplied from a 110 volt to 12 volt tapped transformer, the transformer together with the lamp proving relay is housed in a small cast iron box on the signal pole fixed at eye level, or on an angle iron framework where the signals are mounted on a gantry.
The Platform Homes and Starters are 2-aspect type MV signals fitted with 8 3/8 in. diameter doublet "hotstrip" lenses with SL.17 12 volt double filament rebased lamps. The "hotstrip" is provided to give a "close-up" indication.
Backing, Loop and Dwarf signals are the ME multiple aspect type equipped with 110 volt 25 watt rebased lamps and having 5 1/2 in. inner doublet coloured lens with 6 3/8 in. outer clear spreadlite lenses, green at top, red at bottom.
In the case of double dwarf signals, 3-aspect type ME signals are used having top and bottom lenses green, and the centre a permanently energised red, the indications being either green over red, or red over green depending on which route is selected.
For Dwarf signals reading over more than two routes a special type of combined dwarf signal and route indicator is used having the ME signal type of lens for the signal indication and Box type route indicators consisting of an inner glass having a black background with clear lettering and an outer stippled yellow cover glass, each indication being illuminated with four 110 volt 60 watt lamps.
Call On or Warning signals are 2-aspect ME type having a top 6 3/8 in. doublet green lens illuminated with a 110 volt 25 watt rebased lamp and in the bottom indication a stenciled letter "C" or "W" illuminated with 110 volt 60 watt lamps. These signals are fixed beneath, in the case of pole mounted signals, or at the side of, in the case of gantry signals, their respective Main Line Running Signals.
All Passenger Running Line route indicators are the Box type having clear cut stenciled letters on a black background and an outer stippled yellow cover glass. Each indication is illuminated with four 110 volt 60 watt lamps.
All signal poles are 5 1/2 in. O.D. tubular steel 1/4 in. thick treated with preservative compound inside and supported in cast iron bases fixed to concrete foundations with four I in. x 18 in. foundation bolts. Ladders and guard rings are provided in every case.