In Part I possible methods of improving telegram coil systems for use in a track-to-train communication are examined. These coils are used to convey fixed information, such as the physical limitation of the track on speed, to a moving train. A telegram consists of a number of coils and occurs at various locations along the track. At present only one bit of information is derived per telegram coil and this severely limits the amount of information that can be transmitted, especially in the vicinity of junctions where a lot of information transmission is required. These coils are also restricted to sleeper spacing.