end of the cable pair 24 terminates in an access switch 39 such as the type well known in the art during normal use this access switch 39 is preferably in position a and connects the local end of the cable pair 24 to the normal local load 40 at the local end this local load 40 preferably consists of a device normally used to communicate with the device that terminates the remote end of the cable pair 24 and is well known in the art in accordance with the system and method of the present invention when it is desired to test the cable pair 24 the access switch 39 is preferably operated by moving it to position b this disconnects the normal load 40 replacing it with the testing circuit 60 the testing circuit 60 preferably consists of two separate sinusoidal signal generators 41 and 42 connected in parallel across the cable pair 24 a pair of resistors 43 and 44 each preferably equal to twice the characteristic impedance of the cable pair 24 which preferably serve to match the signal generators 41 42 to the cable 24 and a pair of capacitors 45 and 46 which preferably block any direct current voltage from the sinusoidal signal generators 41 42 also preferably connected as a part of the testing circuit 60 is a frequency selective voltmeter 52 preferably consisting of a bandpass filter 47 an amplifier 48 and a voltmeter 49.