Power Signalling At Bristol
Cables And Wires
The whole area of the interlocking has been divided into locations, all the apparatus and the necessary wiring to and from functions controlled from a location are brought into the welded steel location case. These wires are in all cases single Ancalite insulated wire. The standard sizes adopted are, 1/.064 in. for all signal controls, and 7/0029 in. for all track circuit leads and point control wires. Where the machines are situated a considerable way from the cabin 7/.036 in. wire has been used.
From the location cases to the cabin, paper insulated covered cables have been used; generally there are three cables at each location, one containing all the point controls, one containing all track relay leads, and one containing all signal controls; but if a large number of signals, points, or tracks, are controlled from one location, it is found that the control cables become unduly large in size, in which case two or more cables would be used, each not exceeding 35 cores.
In addition to the three types of cable mentioned above there are the 2-core 110 volt mains which cut into and out of every case, the size varying from 19/.052 in. to a minimum of 7/.029 in. These cables are run along the side of the permanent way on hooks or in wooden trunking as circumstances permit.
In some cases it was found necessary to cross beneath tracks, and here the cables were terminated in a disconnection box at one side of the track, and from the disconnection box large paper insulated lead covered and armoured cables were laid under the track into the cabin where they were straight jointed in the cabin ducts, and brought out as lead covered cables of the same sizes and types as they started from the location.
This procedure was considered necessary as all cables in the cabin were given letter and number references, which were duplicated on the cables at the location case end. This cross referencing permitted easy installation and testing of the cables.