The GIPR & EIR were in the forefront of mechanizing Line Clear process by installing block instruments, Semaphore Signals & Interlocking. Paper line clear tickets are still in use during special circumstances & service disruptions.The list systems of interlocking (G H List) was first introduced in 1892 at six single line crossing stations. The earliest full cabin interlocking arrangements were installed with equipement from Saxby & Farmer devised by John Saxby. The List & Morse system was devised by G H List & A Morse. It was around 1910 track circuits & power signalling (electric & electro-pneumatic) were introduced for points & signals at major stations like Bombay, Calcutta & Madras.