| 摘要 |
1,249,364. Data transmission systems. WESTERN ELECTRIC CO. Inc. 11 Dec., 1968 [14 Dec., 1967], No. 58798/68. Heading H4P. . The redundancy present in a binary signal 41 is removed allowing a reduction in the average transmitted power and removal of line spectra caused by periodic transmission patterns. A bit an has subtracted from it a predicted value Ô n derived from the summed outputs of variable attenuators 43 to which a number of preceding bits are applied from a tapped delay line or shift register 42. The resulting analogue error signal e n is correlated with the delayed bits by multipliers 48 and integrating lowpass filters 47 which control the attenuators 43 in a direction to minimize the error signal. The error signal may be coded for transmission and in this case, since its variance is less than tnat of the input signal fewer bits are required. The receiver, Fig. 5 (not shown), is basically the inverse of the transmitter. The system may also be used for the transmission of multilevel digital signals and analogue samples. |
