METHOD FOR IDENTIFYING MULTIFREQUENCY SIGNALS TRANSMITTED IN DISCRETE FORM Russian patent published in 1999 - IPC

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 μ, 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 N₁, in case it is periodic sequence, to period N₂ < N₁,, both spaced N₂ readings apart, and replacement of input sequence N₁ by resulting sequence of length N₂ < N₁,; (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 k₁ 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