System and method for optimizing termination impedance for an analog telephone line

摘要

A system and method in accordance with a non-limiting aspect minimizes echo return loss in a communications system. The dial tone is broken on an analog telephone line connected to a hybrid circuit having selectable impedance configurations and that interfaces a digital communications circuit and the analog telephone line. A white noise signal as a test call is inserted through the hybrid circuit onto the analog telephone line corresponding to a selected impedance configuration. The returned white noise signal is used for measuring the echo return loss. The test call is dropped. This process is repeated at different impedance configurations to obtain echo return loss measurements at each of the impedance configurations. The optimum impedance setting configuration is determined based on the results and applied to the hybrid circuit and typically set during a running telephone configuration.

主权项

1. A method for minimizing echo return loss in a communications system, the communications system including a hybrid circuit having selectable impedance configurations and that interfaces a digital communications circuit and the analog telephone line, the method comprising:
selecting a simulated balance impedance configuration within a filter connected to the hybrid circuit; simulating balance impedances corresponding to selected impedance setting configurations by loading different coefficients within a transverse digital filter of a CODEC connected between the hybrid and an echo canceller; inserting a test signal through the hybrid circuit onto the analog telephone line; receiving a returned test signal from the analog telephone line through the hybrid circuit and measuring the echo return loss of the test signal corresponding to the selected simulated balance impedance configuration; and determining an optimum balance impedance configuration based on the returned test signal.