Telephone set with howling/echo suppression

摘要

A telephone set has a receiver 1 for outputting a voice in response to a reception signal (i) and a microphone 2 for converting a voice into a transmission signal (g). A frequency indicator 6 cyclically outputs a series of clock signals (a) of different frequencies, and variable band filters 3, 5 respectively filter the reception and transmission signals through band pass filters of which the pass frequency varies according to the clock signals (a). The filtered signals (b), (c) corresponding to each of a cycle of the clock signals are compared by a signal comparator 4, and if the filtered signal levels are equal and of maximum level at one frequency (a), the transmission signal (g) at that frequency is attenuated by a transmission signal controller 7. IMAGE