coded digit track circuit
digit-digit Communication
engineering district；maintenance of way section；track division；track district；track maintenance division
digit by digit algorithm
jointless line；continuously welded rail track；jointless track
non-NTDS track {dummy track}
replacing and laying track with track panel
track-to-track association
track-to-track moving time
transforming single track into double track
double - track existing single track line
a digit synchronized communication net