| 摘要 |
1411859 Audio reproduction PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 12 Feb 1973 [15 Feb 1972 7 April 1972] 6807/73 Heading H4R In a circuit arrangement for producing output signals at a different rate from the input (e.g. for playing back recordings at a speed different from the recording speed), the input signals at 3 are read-in alternately to shift registers 1, 2 via electronic switch S1 at a first rate controlled by clock pulse source f1 and are read-out via electronic switch S2 in phase opposition to S1 at a second rate controlled by clock pulse source f2, the clock sources being connected to the registers through a third, electronic changeover switch S3, S4 synchronized with S1, S2, and register outputs being coupled to their inputs via further electronic switches S5, S6. These latter switches recirculate the stored information to fill-in the gaps produced when read-out from the registers is faster than read-in. Additional or alternative feedback switches S<1>5, S<1>6 may be inserted at selected register output positions to prevent repetition of, e.g. plosives at the beginning of syllables. The electronic switches are MOS transistors possibly integrated with bucketbrigade shift registers and are controlled by unit 5 itself synchronized, e.g. by frequency division from the sources f1, f2. Transistion between register outputs can be smoothed by arranging for the switching of S2' S5 and S6 to be gradual so that during changeover the outputs of both registers read-out together at the same rate f1 or f2. In a modification to improve transition (Fig. 4, not shown) the synchronizing unit 5 for the electronic switches is triggered when both registers are at the same level and are changing in the same direction (i.e. are "in phase") by comparing (13, 23) the last two elements in the registers to produce + ve or - ve outputs which, on coincidence, open a gate (14) to operate a flip-flop (15) triggering unit (5). The changeover switch S3' S4 may be ganged to a switch controlling playback speed of a tape drive motor. |
