Telephone line echo suppressor - monitors mean signal levers on transmission and reception lines and periodically blocks transmission line in dependence on it

摘要

An echo suppressor for a differential network coupling a subscriber to undirectional transmission and reception lines has line base controlled circuits which measure the mean signal power on each line. These are coupled to respective signal detectors and also to a subtractor which generates an error signal of the difference between transmission signal power and a multiple of the reception line power signal representing echo transfer to the reception. The error signal is compared with a preset echo reference level and with the output of the reception line signal detector, to a control circuit and an evaluating circuit. The former controls a blocking circuit in the transmission line to reduce echo while the evaluating circuit, which also receives the transmission signal detector and subtractor outputs, controls the factor by which the reception line power signal is multiplied to reduce the error signal.