Looking at the prototype of my Ulster railways build there is a regular signal just outside a main Belfast station on a sharp bend with a high wall. Because of this there ia a warning signal as you approach the bend and the main signal can't be seen in time so the driver knows what the position is round the bend and wall. It is at the same height of regular signals but is a round disc with a diagonal line. If you understand this query right where can I can get this item?