| 摘要 |
PROBLEM TO BE SOLVED: To provide an alarm indication signal AIS detection circuit with a small circuit scale that detects an AIS when m-consecutive bits of an input signal are '1' and permits n-bit errors in the m-bits. SOLUTION: This alarm detection circuit is provided with a counter 1 that counts number of clocks with consecutive '1s' in input signal data and initializes its count when the input signal data are '0s', a shift register 2 that latches the count of the counter or a value of pre-stage flip-flop circuits 21-2n when the input signal indicates '0s', an adder 3 that totally sums output values of the counter 1 and the shift register 2, and a comparator 4 that compares the result of the adder 3 with a setting value (m-n) and detects an alarm when the result of the adder is higher than the setting value (m-n).
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