Phase difference delay control system for accommodating fluctuation in phase difference in distance measuring system

Abstract

A phase difference delay control system is provided that enables distance measurement between a reference position and a terminal at the time of recovery after a line has been disconnected as a result of fluctuation of phase difference of clock crossover units. In a system for measuring the distance between a reference position and the terminal, first and second interface units comprise respective clock crossover units for sending to a transmission line a signal to which an overhead including phase information for matching the phase of a redundant signal is added, or for sending to the terminal or the reference position the signal from the transmission line, wherein one of the clock crossover units that operate according to the reference clock signal is notified of a fluctuation amount of the phase difference between write and read operation in the other of the clock crossover units and, upon initialization of the phase difference, an initial phase difference is adjusted taking the fluctuation amount into account.