A switching arrangement that can be connected in a communications channel that comprises a pair of lines between sets of terminal equipment, which comprises: (i) a series switch (1,2) for connection in each of the lines; (ii) a shunt switch for connection between the lines; and (iii) a control circuit...http://www.google.fr/patents/US5768341?utm_source=gb-gplus-shareBrevet US5768341 - Communications channel testing arrangement
