Complex sentence: The lines up to Tiruvallur were electrified on 29 November 1979 while the tracks along Platforms 1 to 7 were electrified on 29 December 1979.
Split into simpler sentences: The lines up to Tiruvallur were electrified on 29 November 1979. Platform lines 1 through 7 were electrified on 29 December 1979.