Apparatus for measuring the signal transit time of a digital transmission device

摘要

A signal transmission apparatus includes a higher-level station, a lower-level station and a digital transmission device connected between the stations and having a signal transit time to be measured. Each of the stations has a transmitter for sending useful signals, each clocked by a respective clock signal, through the transmission device to other station. Each of the stations has a receiver for receiving the useful signals clocked by the other station and for separating out the clock signal superimposed on the applicable useful signal. The useful signal to be transmitted in the higher-level station is clocked by a given clock signal. The useful signal to be transmitted in the lower-level station is clocked by a clock signal derived from the clock signal separated out from the receiver of the lower-level station. The higher-level station has a phase comparator for comparing the given clock signal with the clock signal separated out by the receiver of the higher-level station and supplying a comparison outcome. The higher-level station has an arithmetic unit for calculating the signal transit time from the comparison outcome.