Dual hysteresis signal detection circuit

A circuit for detecting a duration of an input signal, comprising:

• a first band pass filter for inputting said input signal and outputting a first signal having a first frequency;
• a second band pass filter for inputting said input signal and outputting a second signal having a second frequency;
• a first hysteresis comparator electrically coupled to said first band pass filter for comparing with said first frequency of said first signal to output a first square wave signal according to a first high voltage and a first low voltage;
• a second hysteresis comparator electrically coupled to said first band pass filter for comparing with said first frequency of said first signal to output a second square wave signal according to a second high voltage and a second low voltage;
• a third hysteresis comparator electrically coupled to said second band pass filter for comparing with said second frequency of said second signal to output a third square wave signal according to said first high voltage and said first low voltage:
• a fourth hysteresis comparator electrically coupled to said second band pass filter for comparing with said second frequency of said second sianal to output a fourth square wave signal according to said second high voltage and said second low voltage;
• a first detection circuit electrically coupled to said first hysteresis comparator and said third hysteresis comparator for detecting a part of said first signal having said first frequency and a part of said second signal having said second frequency that are higher than said first high voltage and lower than said first low voltage to output a first detection signal according to said first square wave signal and said third square wave signal;
• and
• a second detection circuit electrically coupled to said second hysteresis comparator and said fourth hysteresis comparator for detecting a part of said signal first having said first frequency and a part of said second signal having said second frecuency that are higher than said second high voltage and lower than said second low voltage to output a second detection signal according to said second square wave signal and said fourth square wave signal;
• said duration of said input signal being detected according to said first detection signal and said second detection signal.