LINE DISCRIMINATION DEVICE, METHOD AND DEVICE FOR DISCRIMINATING EXISTENCE OF FUNCTION OF TELEPHONE LINE, AND METHOD AND DEVICE FOR EXAMINING EXISTENCE OF SERVICE TO TELEPHONE LINE IN FIELD

摘要

PROBLEM TO BE SOLVED: To provide a method and a device for discrimination which a telephone line engineer can use to discriminate laid services by examining a telephone line in the field. SOLUTION: A tuning circuit having a specific resonance frequency responds to a test signal which is inputted to the line and has a specific resonance frequency with an excitation signal, and a modulator modulates the excitation signal when the test signal exists. Alternatively, an interrogative test signal including a specific frequency is inputted to the telephone line, and the excitation signal from the tuning circuit is detected in response to this specific frequency. Alternatively the telephone line is monitored with respect to the input of the test signal including a specific frequency component, and the characteristics of the test signal in the specific frequency are increased at the time of detection of the test signal on the telephone line.