摘要:
PROBLEM TO BE SOLVED: To provide an analog line terminal capable of correctly receiving signals from a corresponding party even when a line echo extending as much as hundreds of milliseconds occurs.SOLUTION: Each signal level of plural input signals received via an analog line 20 connected to a communication network is compared with a signal level of a received signal received just before or with a history of signal levels of input signals received from a corresponding party terminal in the past by a level detection unit 13. If the former exceeds a threshold x-dB predetermined for a signal level of an input signal received just before or a second threshold y-dB predetermined for a history of signal levels of input signals received from the partner terminal in the past, the analog line terminal 1 abandons the input signal regarding the input signal as a line echo of a transmission signal transmitted by the analog line terminal 1, and causes a signal transmission reception unit 12 to perform reception processing on the signal whose signal level is within the threshold x-dB or the second threshold y-dB as proper input signals from the partner terminal.
摘要:
An echo preventing circuit comprises a filter that is inputted with a first digital signal and outputs a second and a third digital signals; a first DA converter that converts the second digital signal into a first analog signal and outputs the first analog signal; a second DA converter that converts the third digital signal into a second analog signal and outputs the second analog signal; an input/output terminal that outputs the first analog signal or that is inputted with a third analog signal; a subtracting circuit that outputs a fourth analog signal obtained by subtracting the second analog signal from a signal formed by combining the first analog signal and the third analog signal; and an AD converter that converts the fourth analog signal into a fourth digital signal and outputs the fourth digital signal, wherein the filter sets filter coefficients for which the fourth analog signal is a signal formed by removing or attenuating the first analog signal from a signal formed by combining the first analog signal and the third analog signal, based on the fourth digital signal outputted from the AD converter when signals are inputted into the first and the second DA converters while the third analog signal is not present, and wherein the fourth analog signal outputted from the subtracting circuit is outputted as an output signal corresponding to the third analog signal.
摘要:
PROBLEM TO BE SOLVED: To reduce feeling of echo in the subsequent conversation even when a tone signal is input. SOLUTION: The echo canceler uses an adaptive filter for generation of a pseudo echo and removes an echo using a hybrid circuit. The echo canceller includes a tone type determining means for determining whether a remote end input signal is a predetermined type of tone signal, and a band stop filter provided at an input stage of the adaptive filter for removing a frequency component of the determined predetermined type of tone signal from the remote end input signal to the adaptive filter when the tone type determining means determines that the remote end input signal is the predetermined type of tone signal. COPYRIGHT: (C)2011,JPO&INPIT