Analog telephone line equipment testing method, involves opening line test relay to isolate line equipment and closing ringing relay to apply ringing signal such that input amplifier is saturated for generating high level harmonics

摘要

The method involves opening a line test relay (103) to isolate a telephone line equipment and closing a ringing relay to apply a ringing signal such that an input amplifier is saturated for generating high level harmonics in a telephone bandwidth. The harmonics are detected either in a coder-decoder or in a controller (117) of an autoswitch, to test the operation of a ringing circuit. An independent claim is also included for an analog telephone line equipment.