A method for measuring the overall loss in four-wire phone circuits, and apparatus for carrying it out

摘要

The remote ends of two pairs of conductors forming a four-wire circuit are directly connected. A phonic signal is applied to the near end of one pair of conductors, and the logarithmic level of resulting signal is measured at the near end of the other pair of conductors. A compandor, adapted to reduce the logarithmic level of a signal by a fixed division factor is then inserted between the remote ends, and a phonic signal is again applied to the near end of one pair of conductors and the logarithmic level of the resulting signal is then measured at the near end of the other pair. Mathematical relations are used to obtain the overall loss for each separate pair of conductors.