| 摘要 |
PURPOSE:To reduce the effect of temperature change and to attain high speed processing by using a clock having a frequency being twice or over of the transmission speed so as to apply analog/digital conversion processing to an analog input signal, converting it into a digital signal, processing it digitally and setting a digital identification level to apply code identification. CONSTITUTION:An analog input 41 is converted into n-bit digital signal sampled by an operating clock 46 and fed to one input of a digital comparator 43. The result of addition from a digital adder 49 being one of identification level setting circuits is fed to the other input of the digital comparator 43. Then the digital comparator 43 compares the quantity of two inputs and if the output of the A/D converter 42 is larger than the output of the digital adder 49, a high level is outputted and a low level is outputted when the output of the A/D converter 42 is smaller. Thus, the automatic adjustment is applied to obtain an optimum identification level. Moreover, even when a level exists only at prescribed period, a gate signal corresponding to the existing period is given to store the identification level completely other than the existing period and the circuit is operated as if it were in existence continuously.
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