In the good old days, as the last millenium was coming to a close, the trains moved around without communications. No Signals existed and Engineering department took necessary action.
• Telegraph & Telephony progressively came into existence in India through Railways requirements. Earliest lines sanctioned in the direction of Rail routes was from Calcutta to Peshawar and Bombay area.
• Signal Engineer first appointed by the Ex East Indian Railway was Mr S.T.Dutton in 1889.
• Indian system of Interlocking by Mr G.H.List in 1892 at six single line crossing stations of NorthWestern Railway took in the form of a detector locking apparatus for protecting the facing points of trains moving at high speed.
• Cabin Interlocking as invented by John Saxby and existed in the British Railways adopted in 1893 and installed by Messrs Saxby & Farmer (India).
• List & Morse system in collaboration with Mr A.Morse in 1894 at 28 single line crossing stations between Lahore & Ghaziabad.
• Signal Engineer appointed in the Great Indian Peninsula Railway appointed Mr I.W.Stokes, in 1903.
• Heppers Key Electric key transmitters was invented by Major (Later Sir Lawless) Hepper, signal Engineer, Ex North Western Railway to replace key interlocking by hand who eventually became the General Manager of the Ex Great Indian Peninsula Railway.
• Double wire signalling was developed by Mr E.W Baker, Signal Engineer Ex Assam Bengal Railway for operating points and signals by steel wires and replace rodding and was first used on Southern & North Eastern Railways.
• Large scale Cabin interlocking was adopted on Bombay-Delhi route and completed by the Great Indian Peninsula Railway in 1912.
• Track Circuiting was developed in early 19th Century.
• Power Signalling was developed in early 19th Century to operate points & signals electrically or electro pneumatically .
• Power Signalling & Track circuiting was used at busy stations like Bombay, Calcutta & Madras.
• Block Instrument developed for single line by Mr Neale, an Engineer of the Great Indian Peninsula Railway called Neale Block Token.
(Source: Official Indian Railway site)