APPARATUS FOR AUTOMATICALLY SETTING IMPEDANCE OF SUBSCRIBER MATCHING CIRCUIT BALANCING NETWORK OF SWITCHING SYSTEM

摘要

PURPOSE: An apparatus for automatically setting an impedance of a subscriber matching circuit balancing network of a switching system is provided to reduce an echo factor and maintain a good speech quality by setting an impedance according to a characteristic impedance of a subscriber's line. CONSTITUTION: A hybrid coil(10) converts mutually two analog lines and four digital lines. A balancing network(20) sets characteristic impedance of a subscriber's line. A characteristics impedance measuring unit(30) automatically measures a characteristics impedance of a corresponding subscriber's line. A controller(40) transfers a value of the measured characteristic impedance to the characteristic impedance measuring(30) and to the balancing network(20). The balancing network(20) is formed as a bridge with a resistance component(R) and a capacitance component(C). When the characteristic impedance measuring unit(30) measures a characteristic impedance at the initial time of installation of a line and inputs a corresponding value to the controller(40), the controller(40) commands the balancing network(20) to form a bridge having a resistance and a capacitance corresponding to the value. For the impedance measurement of the characteristic impedance measuring(30) and the connection of the controller(40) and the balancing network(20) of a subscriber matching circuit(50) to the bridge, a test bus for testing the subscriber matching circuit(50) is utilized.