METHODS OF AND APPARATUS FOR DETERMINING ELECTRICAL CHARACTERISTICS OF TRANSMISSION LINES

摘要

METHODS OF AND APPARATUS FOR DETERMINING ELECTRICAL CHARACTERISTICS OF TRANSMISSION LINES Apparatus is disclosed for automatically measuring accurately and rapidly alternating and direct voltages, resistance, and capacitance of a telephone line. Direct voltages and relatively high resistances can be determined by filtering out 60 Hz a.c. signals and measuring line current with and without a voltage source connected in series with the line. Capacitance is measured by charging the line from the voltage source, discharging the line into a plurality of integrators having different time constants, and sampling the output voltage of one of the integrators after a respective integral number of 60 Hz periods. The integrator whose output voltage is sampled depends on the capacitance being measured. The resultant measurement is corrected in respect of voltages on the line by performing a second integration without again charging the line, and the corrected result is modified to take into account the previously measured resistance of the line.