Apparatus for remotely measuring characteristics of a communications line including: receiver means for connection to a remote end of the communications line; sender means for connection to the other end of the communications line, said receiver means including a signal generator for generating a signal in use which is transmitted along the communications line toward the sender means said sender means having detection means for detecting said signal; and switching means; wherein: said signal is generated in response to a selection of one of a plurality of characteristics of said line to be measured; said signal uniquely representing said selected characteristic, such that on detection of said signal and, on the basis of the unique representation of the signal, the switching means is controlled so as to connect corresponding circuitry across the line at said other end; and wherein: in response to said selection of one of a plurality of characteristics of said line to be measured, in the receiver, a circuit corresponding to the selected characteristic is selected from a plurality of selectable circuits and connected across said remote end to enable the selected characteristic of the line to be measured. receiver means for connection to a remote end of the communications line; sender means for connection to the other end of the communications line, said receiver means including a signal generator for generating a signal in use which is transmitted along the communications line toward the sender means said sender means having detection means for detecting said signal; and switching means; wherein: said signal is generated in response to a selection of one of a plurality of characteristics of said line to be measured; said signal uniquely representing said selected characteristic, such that on detection of said signal and, on the basis of the unique representation of the signal, the switching means is controlled so as to connect corresponding circuitry across the line at said other end; and wherein: in response to said selection of one of a plurality of characteristics of said line to be measured, in the receiver, a circuit corresponding to the selected characteristic is selected from a plurality of selectable circuits and connected across said remote end to enable the selected characteristic of the line to be measured. said signal is generated in response to a selection of one of a plurality of characteristics of said line to be measured; said signal uniquely representing said selected characteristic, such that on detection of said signal and, on the basis of the unique representation of the signal, the switching means is controlled so as to connect corresponding circuitry across the line at said other end; and wherein: in response to said selection of one of a plurality of characteristics of said line to be measured, in the receiver, a circuit corresponding to the selected characteristic is selected from a plurality of selectable circuits and connected across said remote end to enable the selected characteristic of the line to be measured. in response to said selection of one of a plurality of characteristics of said line to be measured, in the receiver, a circuit corresponding to the selected characteristic is selected from a plurality of selectable circuits and connected across said remote end to enable the selected characteristic of the line to be measured.