| 摘要 |
The present invention is directed to a facsimile system incorporating a digital filter, which digital filter is used to detect the presence of a start signal and a stop signal in an input signal, which start and stop signals control the starting and stopping of the facsimile system. The digital filter used in the facsimile system of the present invention includes an electronic switch which is switched under the control of a reference signal. An input signal is also applied to the digital filter and the digital filter provides for an output signal when there is a frequency correlation between the reference signal and the input signal. The digital filter provides a very sharp response and does not use impedance elements to determine the tuning of the filter. The impedance elements used in the digital filter only control the time constant of the filter.
|
