| 摘要 |
PURPOSE:To prevent the echoes of a conference telephone device by discontinuing a subtracting action of an artificial echo signal in case a microphone is switched off when an artifical echo signal is produced from an input signal of the reception side and then subtracting the artificial echo signal from an actual echo signal. CONSTITUTION:An input signal (x) supplied from an input termianl 16 is delivered through a speaker 13. When a mike switch 2 is closed, the signal (x) delivered through the speaker 13 is collected by a mike 1 and turned into an echo signal (y). At the same time, the signal (x) is supplied to a delay circuit 10 with taps. Then the signal (x) is turned into an artificial echo signal (y') via an echo model part 11, etc. The echoes can be erased by subtracting the signal (y') from the signal (y). when the switch 2 is opened, no signal (y) is produced. A decision control circuit 4 decides the state of the switch 2 and sets the signal (y') at zero. As a result, it is avoided to deliver the signal (y') only. |
