The present R.R.I. (Route Relay Interlocking) panels is not provided with a
D.S.(Train Describer System) i.e. Train numbers(id’s) are not shown in the panel .The Panel controller of each station has been provided with a time table on a day to day basis which contains the train IDs.
R.R.I. will soon give way to S.S.I.(Solid State Interlocking).In this type of interlocking three computers are present. Two computers will have 3 inputs coming from the field. These are:
Various aspects of signals present at the station.
Position of Points (whether normal or reverse).
Condition of Track circuits (Occupied or released).
The o/p of both the computers is given to a third computer which acts as a comparator. To set a route for an incoming train the third computer will compare the outputs from both the computer and if they match then only the corresponding route will be set.
S.S.I. is implemented in Indian Railways at smaller stations.