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    • 2. 发明授权
    • Digital measurement of the DC value in an AC signal adapted to telephone
off-hook detection
    • 数字测量适用于电话摘机检测的交流信号中的直流值
    • US4132864A
    • 1979-01-02
    • US792079
    • 1977-04-28
    • Joseph S. Feng
    • Joseph S. Feng
    • H04M3/02H04M3/06H04M19/02H04M3/22G04F9/00
    • H04M19/026
    • The duty cycle of an AC telephone off-hook signal is measured by means of comparing it with the duty cycle of a known AC signal having a duty cycle of 0.5 because it has a DC component of zero. Measurement of the duty cycle in a telephone off-hook detector application involves measuring the DC portion of the signal on a pair of telephone lines from a telephone handset to an exchange. A high frequency master clock oscillator with a much higher frequency than the basic ringing voltage is used. An input signal is used to gate clock pulses to a counter when the input signal is positive. At the end of a predetermined number of clock pulses, the counter is gated into memory connected to a decoder for transmission of the decoded signal to the exchange for appropriate action.
    • 通过将AC电话摘机信号的占空比与占空比为0.5的已知交流信号的占空比进行比较来测量,因为其DC分量为零。 电话摘机检测器应用中占空比的测量涉及测量从电话听筒到交换机的一对电话线上的信号的直流部分。 使用高于基本振铃电压的高频主时钟振荡器。 当输入信号为正时,输入信号用于将时钟脉冲输入到计数器。 在预定数量的时钟脉冲结束时,计数器被选通到连接到解码器的存储器中,用于将解码信号传输到交换机以进行适当的动作。