Conference telephone system

Abstract

Abstract PURPOSE:To offer a conference telephone system including a howling prevention circuit without deterioration of talking quality such as interruption of voice by the application of an echo canceller used for satellite communication. CONSTITUTION:A signal from a 2-wire telephone line 10 is converted into a 4- wire signal by a 2-wire/4-wire converter 1. After the converted reception signal is converted into a digital signal by an A/D converter 2, the converted result is fed as a transmission signal of the 1st echo canceller 3. The transmission output of the 1st echo canceller 3 is given as the reception input to the 2nd echo canceller 4 and also restored into an analog signal by a D/A converting circuit 5 again and electroacoustic-transduced by a speaker 6. It is possible to suppress the sound coupling between microphones and the sneaking to the transmission incoming reception side at the 2/4-wire converter 1 by 20-30 dB respectively, and since no howling is produced even when the sound volume of the speaker and the sensitivity of the microphones are increased without using a voice switch, the conference telephone with natural sound volume is attained.

Inventors

• 👤 Yoshiji Furuya
• 👤 古屋　宣二
• 👤 Yasuo Ito
• 👤 泰雄 伊藤

Bibliographic Details