Very nice DSP sir I understood somethings from above message so In general interlocking means I take example of Generators for my easyness so These Gen sets are interlocked with each other so that one can run in failure of other but both shud not be run at same time so in same way one line on which train stood shud be red in the SM station control panel and remaining will be Green so that SM can see where to take another train in which loop line. And also All lines are interlocked with each other so that SM can operate one line and all other get automatically operated where it avoids one by one operation to SM and makes controlling clumsy and leads for unsafety or accidents. Am I right in this concept?