A METHOD FOR OFF-HOOK DETECTION DURING RINGING AND THE USE OF A SUBSCRIBER LINE INTERFACE CIRCUIT FOR OFF-HOOK DETECTION DURING RINGING.

摘要

A method for off-hook detection at a subscriber line interface circuit upon the occurence of a ringing signal which preferably lacks a direct current component, as well as the use of a subscriber line interface circuit for the performing of said method, comprising the steps of generating a signal which is a function of the line current (il) through the subscriber line, measuring the time ('DELTA't) the signal exceeds a first reference value (Vth), which represents a predetermined current value, comparing the measured time ('DELTA't) with a predetermined time value and indicating off-hook in a processor in dependence of the comparison.