FIELD: radio engineering, equipment for information transmission systems with frequency modulation, communication systems with pseudorandom operation frequency change, in particular. SUBSTANCE: technical result lies in reduced time of tuning to operation frequency which is achieved by execution of following operations with signal: formation of periodic signal proportional to sine of input frequency, formation of periodic signal proportional to cosine of input frequency, multiplication of signal proportional to sine of input frequency by coefficient K1, that is set across first controlling input of demodulator and is computed by formula K1 = cos(2πfnT) where fn is required tuning frequency of demodulator; T is delay time of signal in delay line. Then signal proportional to cosine of input frequency is multiplied by coefficient K2, that is set across controlling input of demodulator and is computed by formula K2 = sin(2πfnT). Discrimination characteristic with center on frequency fn. is formed with subtraction of obtained signals. Change of tuning frequency of demodulator is carried out by change of coefficients K1 and K2. Change of tuning frequency of demodulator occurs practically instantaneously after change of coefficients K1 and K2 since multipliers and adder are inertia-free elements. EFFECT: reduced time of tuning to operation frequency. 1 dwg
