| 摘要 |
PURPOSE:To obtain a device generating digitally audible tone such as dial tone used for a telephone exchange by storing only a binary value corresponding to one sampling period of a signal to be generated to execute complex number operation sequentially. CONSTITUTION:Two numbers given as a=cos(2pif/f0) and b=sin(2pif/f0) are stored respectively in memories as linear binary numbers, where (f) is a signal frequency and f0 is a sampling frequency. Initial values 1, 0 are set respectively to registers 5, 6 at first and then an output of adders A1, A2 is stored respectively. Further, multipliers M1, M2, M3 and M4 are provided and then, the real part of a number powered to (a+jb) is outputted to the adder A1, the output of the A1 is multiplied by K at a multiplier M5 to be matched to the compressing mode of PCM at a linear-nonlinear converting section 7. The output of the adder A1 corresponds just to the sampling value of the cosine wave. |
