METHOD FOR DETECTING OCCURRENCE OF CHANGE IN LINK FROM STATION OF TERMINAL

摘要

PROBLEM TO BE SOLVED: To provide a method for detecting whether an NIU(Network Interface Unit) is bypassed or bridged.;SOLUTION: In the method, the change in the characteristic impedance of an incoming cable to which the NIU is connected is detected by testing a reflection signal that exists when a signal sent to a head end is not connected to a coaxial cable that is properly connected to the link. Especially, the phase of a transmission signal from the NIU is compared with the phase of the reflection signal, thereby discriminating whether it is the signal propagated by a distance before being reflected and returned or the signal immediately reflected in the vicinity of a connector of the NIU. Only the latter signal is used for excitation (stimulation) denoting the change. The important difference between the two kinds of the reflection signals is a time delay of the reflection signal with respect to the signal transmitted from the NIU.;COPYRIGHT: (C)2002,JPO