Telephone line characteristic display

摘要

There is disclosed a telephone line characteristic measuring instrument of the type described in U.S. Pat. No. 3,814,868, provided with an oscilloscope display. A signal representing the impairments induced on a test tone by a tele-communication transmission facility, without the test tone itself, is applied to the vertical deflection plates of an oscilloscope. The test tone, or one of its harmonics, is applied to the horizontal deflection plates. The resulting Lissajous patterns identify the source of a disturbance (e.g., amplitude modulation, phase modulation, white noise, etc.).