| 摘要 |
FIELD: communications engineering. SUBSTANCE: method for identifying multifrequency, two-of-eight or two-of-six coded signals transmitted over digital communication channels among telephone exchanges in digital form using pulse-code modulation obeying law A or ??, additive differential pulse-code modulation, and delta modulation but pre-transformed into pulse-code modulatio format involves following procedures: (a) addition of input discrete sequence of length N<SB>1</SB>, in case it is periodic sequence, to period N<SB>2</SB> < N<SB>1</SB>,, both spaced N<SB>2</SB> readings apart, and replacement of input sequence N<SB>1</SB> by resulting sequence of length N<SB>2</SB> < N<SB>1</SB>,; (b) frequency decimation of sequence being processed in case its length N is even number or number N and number of discrete Fourier transform component k<SB>1</SB> corresponding to probable sine-wave frequency in desired set of multifrequency signal have highest common divisor other than unity; (c) calculation of squares of modules of eight or six discrete Fourier transform components of input signals by using Hertzel algorithm that includes arithmetic operations with real numbers only; (d) selection of two of them having highest value. EFFECT: reduced number of arithmetic operations required for identifying multifrequency signals. 1 dwg
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