Briefly, the foregoing objects, and other objects and advantages that will be apparent to those of ordinary skill in the art, are achieved by the use of a method for detecting whether the frequency fi of {TAIL ~ a tone signal} is within {HEAD ~ a passband fb} surrounding a desired detection frequency fd 
Briefly , the foregoing objects , and other objects and advantages that will be apparent to those of ordinary skill in the art , are achieved by the use of a method for detecting whether the frequency fi of { TAIL ~ a tone signal } is within { HEAD ~ a passband fb } surrounding a desired detection frequency fd
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