HOWLING PREVENTION CIRCUIT FOR LOUDSPEAKER SYSTEM TELEPHONE SET

摘要

PURPOSE:To realize a loudspeaker system telephone set with excellent talking quality by suppressing echo by a 1st echo canceller circuit based on a signal at a band being a half the voice band and using a 2nd echo canceller circuit so as to suppress the echo based on the signal of the remaining band. CONSTITUTION:The voice signal is separated into a 1st band (low frequency component) signal s1(k) and a 2nd band (high frequency component) signal s2(k) at a 1st band separation filter 41. Moreover, the high frequency component s2(k) is added to a pseudo echo signal in the 2nd echo canceller circuit. The pseudo echo signal is obtained by suplying the reception signal high frequency component r2(k) to the 2nd echo canceller circuit 53. The low frequency component s1(k) of the transmission signal is inputted the 1st echo canceller circuit 51 to generate a pseudo echo signal and added to the 1st band signal r1(k) separated by the 2nd band separation filter 45. Thus, the gain of the entire voice band is suppressed to prevent production of howling.