Complex sentence: At one time, all tracks were electrified with the NH-PRR standard 11 kV 25 Hz overhead catenary; the passenger tracks since 1917, and the freight tracks from 1927 to 1969.
Split into simpler sentences: At one time, all tracks were electrified with the 11 kV, 25 Hz overhead catenary, the standard of NH and PRR. The passenger tracks have been electrified since 1917, and the freight tracks from 1927 to 1969.