PURPOSE: To stably judge whether a voice system in a video conference is in a transmitting state or a receiving state.
CONSTITUTION: An echo canceller 12 and a transmitting signal attenuator 14 are provided for on a transmission line. A receiving volume adjuster 18 and a receiving signal attenuator 20 are provided for on a reception line. The input level of the transmitting signal from the preceding stage of the echo canceller 12 is detected by a transmitting input level detector 13, and the input level of the receiving signal is detected by a receiving input level detector 19. The detected outputs of the transmitting input level detector 13 and the receiving input level detector 19 are supplied to a comparator 15. Then, a control execution from the comparator 15 is supplied to the transmitting signal attenuator 14 and the receiving signal attenuator 20. Also, the attenuating amounts of the transmitting signal attenuator 14 and the receiving signal attenuator 20 are adjusted according to the adjusting amounts of the receiving volume adjuster 18.
IMADA MASANORI
HANAMURA KIYOSHI
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