| 摘要 |
PURPOSE:To stop the operation of an echo controlling device, by providing a frequency analyzing circuit, deciding circuit, and control circuit and detecting the non-sound signal of an MODEM, facsimile, etc., which do not send any conditioning tones. CONSTITUTION:An input signal from an input terminal is divided into four bands of 0-850Hz, 850-1,700Hz, 1700-2,550Hz, and >=2,550Hz by filters 21, 22-24 of a frequency analyzing section 2 and signals of each band are measured in terms of the level by signal level measuring instruments 25, 26-28. These measured outputs are sent to a deciding section 3 where the intensity of signals of each band is compared and their order is determined by means of a comparator circuit 31. Then a deciding circuit 32 decides whether an input signal is a sound signal or non-sound signal in accordance with a previously stored deciding criterion. A control circuit 4 detects the non-sound signal of the MODEM, facsimile, etc., which do not send any conditioning tones by using the decided result and can stop the operation of an echo controlling device. |
