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    • 1. 发明授权
    • Digital multi-frequency receiver
    • 数字多频接收机
    • US4328398A
    • 1982-05-04
    • US148232
    • 1980-05-09
    • Masaharu KawaguchiYoshikatu ShiraishiKazuhiro MaruyamaHitoshi ImagawaYoshimasa Kaneko
    • Masaharu KawaguchiYoshikatu ShiraishiKazuhiro MaruyamaHitoshi ImagawaYoshimasa Kaneko
    • H04Q1/457H04M1/50
    • H04Q1/4575
    • A digital multi-frequency receiver for the use in an electronic telephone exchange system for detecting MF signals (700,900, 1100, 1300, 1500 and 1700 Hz) in the CCITT No. 5 system. The digital multi-frequency receiver comprises a recursive digital filter for detecting each of the MF signals on a time divisional basis, an absolute value circuit for providing the absolute value of the output of the recursive digital filter, a comparator for comparing the output of the absolute value circuit with a variable threshold to provide the detected MF signal information, and a circuit for providing the variable threshold by selecting the maximum value from among, (i) the predetermined fixed value, (ii) the product of the value .alpha. which is less than but close to 1 and the maximum value of the variable threshold circuit in a preceding frame, and (iii) the maximum value of the output of the absolute value circuit in a present frame.
    • 一种用于电子电话交换系统中用于检测CCITT 5系统中的MF信号(700,900,1100,1300,1500和1700Hz)的数字多频接收机。 数字多频接收机包括用于基于时分检测每个MF信号的递归数字滤波器,用于提供递归数字滤波器的输出的绝对值的绝对值电路,用于将递归数字滤波器的输出进行比较的比较器 具有可变阈值以提供检测到的MF信号信息的绝对值电路,以及用于通过从(i)预定固定值中选择最大值来提供可变阈值的电路,(ii)值α的乘积, 小于但接近1,并且前一帧中的可变阈值电路的最大值,以及(iii)当前帧中的绝对值电路的输出的最大值。