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 {HEAD ~ the frequency fi} of a tone signal is within {TAIL ~ a passband fb} surrounding a desired detection frequency fd 
is within
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 { HEAD ~ the frequency fi } of a tone signal is within { TAIL ~ a passband fb } surrounding a desired detection frequency fd
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