| 摘要 |
PURPOSE:To attain ease of synchronism and to prevent generation of noise by providing a Fourier transform circuit, a spectrum modifying circuit and an inverse Fourier transform circuit to a privacy call equipment to simplify the device constitution and prevent a spectrum from being spread. CONSTITUTION:A voice signal from an input terminal 1 is subjected to A/D conversion 2 and fed to a multiplier 5 via buffer memories 3, 4 comprising shift registers. An output of a prescribed bit of the multiplier 5 is fed to the Fourier transform circuit 6 and a multiplier 7 by using a timing clock. Each signal is subject to Fourier transform by the transform device and the multiplier 7 to apply frequency conversion to the time axis and the spectral form is detected by the spectrum modifying circuit 8. The output is fed to the inverse Fourier transform ciruit 10 via a multiplier 9, a signal replaced optionally is subject to inverse Fourier transform to apply inverse tranform of the frequency axis into the time axis. Then the signal is processed by a multiplier 11, the buffer memories 12, 13 and a D/A converter 14 and the result is outputted. |
