There, a piece of hardware called the concentrator unit plucks the data off a fiber-optic network, reformulates it into a signal at 2 to 30 megahertz and injects that signal onto the power line.

FORBES: Magazine Article

Network Rail has upgraded power supplies and signalling systems and lengthened 41 platforms at 12 stations on the Midland main line north of London to accommodate the new trains which are nearly 270 yards (250m) long.

BBC: Longer trains set to ease congestion on Thameslink line