A device for checking a transmission line carrying a plurality of digital and/or analogue transmission channels is provided. The device includes a measurement block designed to evaluate performances, search for faults and determine the quality of the line and services transmitted through the said line. A system for measuring disturbances is also provided. The system measures disturbances in a transmission line firstly connecting a subscriber to a high speed server through an xDSL modem, and secondly to a switched telephone network.