Loud speaker telephone set system

Abstract

Abstract PURPOSE: To control a value of a variable attenuator to a required minimum value not causing howling and glocking according to the usage conditions, by converting each control signal inputted to a loud speaker telephone set to a digital signal and operating this signal. CONSTITUTION: A transmission input signal (ti) and a reception input signal (ri) are converted into a transmission level signal (tc) and a reception level signal (rc) respectively at rectifying/smoothing circuits 11, 12, and they are inputted to an A/D converter 61 together with a reception audio adjusting signal (vc) and converted into a digital signal (dc). A control circuit 62 obtains the transmission and reception input levels from the digital signal (di) for operation to obtain the insertion attenuation of the channel and reception line, and a variable attenuator 63 in the transmission line and a variable attenuator 64 in the reception line can respectively be controlled with the digital control signals (dt) and (dr). COPYRIGHT: (C)1982,JPO&Japio

Inventors

• 👤 Masakazu Nishino
• 👤 Hisashi Fujisaki

Bibliographic Details