SCRAMBLING SYSTEM OF VOICE SIGNAL

摘要

PURPOSE:To realize scrambling of a voice signal, to simplify the constitution of a receiver side and to decrease the cost by mixing a voice signal with a prescribed carrier signal and applying FM modulation to the voice carrier with the lower-side band component produced by the mixing to transmit the result. CONSTITUTION:A lower-side band component B-A and an upper-side band component B+A are produced in an output of a mixer 1 mixing the voice signal A with a prescribed carrier signal B. Only the upper-side band component B-A in two kinds of the side-band components is transmitted through a low-pass filter 3. Only the lower-side band component obtained in this way is modulated by an FM modulator 4 of 4.5MHz, an output of the FM modulator 4 is mixed with a video carrier further to transmit the upper-side band. The A and the 2B-A components are generated by mixing the B-A component subjected to FM demodulation with the carrier signal B from an oscillator 7 at a mixer 6 through a low-pass filter 5 and only the A component is obtained as a voice signal by a low-pass filter 8.