| 摘要 |
<p>A method and apparatus for detecting the presence or otherwise of a particular frequency component in a pulse coded multi-frequency signal in which ones of the pulse sequence representing the signal are multiplied separately by ones of two pulse sequences representing the frequency of said particular frequency component for two relative phase displacements other than 0 and n pi (n=1,2,3 . . . . ), summing the two sets of multiplicands so obtained and comparing at least the greater sum so derived, or functions of these sums with a reference value.</p> |
