A set of four, full sized, Train Protection Warning System (TPWS) grids allowing for both an Overspeed Sensor System (OSS) and a Train Stop System (TSS) to be fitted for a single signal.
These grids are designed to be fitted to Hornby track (or any other make of track in which the centre of the sleepers are 7mm apart). Note that the grids are not evenly placed across the support bars; there is a small dimple on the underside at one end of each grid. These marked ends should be touching when two grids are fitted together to form a TSS.
Fitting of the Train Protection Warning System (TPWS) was mandated under railway safety regulations introduced in 1999. TPWS is primarily designed to prevent high speed head-on or side-on collisions. It does not help prevent rear-end collisions. Exact placement of the activation grids are dependent upon the speed limit imposed on the line. For full details see this detailed description.