Fast and highly precise measuring method for subscriber lines

A reduction of the time required to measure telephone subscriber lines is needed to rationalize the operation and maintenance of the communication networks and facilities. A subscriber line has an impedance of resistance and capacitance connected in series and in parallel. The conventional method required several seconds to charge and discharge the line to prevent incorrect ringing of the telephone during measurement, and the measurement precision was not high. A measuring instrument that measures subscriber lines promptly and precisely using a voltage-controlled power source, a high-speed voltage/current measuring circuit, and digital signal processing technique is presented. This instrument completes all subscriber line measurements is one second, as compared with ten to twenty seconds required by the conventional equipment