| 摘要 |
<p>836,235. Electric selective signalling apparatus. WESTERN ELECTRIC CO. Inc. April 26, 1957 [April 27, 1956], No. 13350/57. Class 40 (1). [Also in Groups XIX and XXXV] A digital-to-analogue converter consists of a cathode-ray tube with a perforated target containing rows of binary digital coded numbers in which the beam is deflected until the row of numbers selected corresponds to the coded input address. There is an additional control of fine positioning of the beam with respect to the selected row of apertures. The resultant control voltage necessary to effect the deflection represents the analogue output and is used to control one axis of the beam deflection system of an information storage tube. The second axis is controlled by a similar arrangement. In one embodiment, for a 5-digit code, the input address, applied in parallel form to a register 17, is converted to an analogue voltage at 18 and after amplification at 19 applied to the deflection plates 15 of the cathode-ray tube 10 so as to position the beam vertically on the code plate 13. The digital output obtained from the targets 26 ... 30 by scanning the beam horizontally is compared at 31, Fig. 2 (not shown), with the original address and any error, amplified at 32, is applied to the amplifier 19 to move the beam to the correct position on the plate 13. Anadditional quantizing set of apertures 30 provide an output for centralizing the beam with respect to the selected row of code apertures. In a second embodiment, Fig. 3, a three-digit code address applied to a register 17 is subtracted at 49 from the output of the targets 27 ... 29 of the coding tube. If the two code signals are not in agreement, then an output is produced in respect of each incorrect digit, and this output controls the appropriate one of 3 current generators 43 ... 45. The generators are " weighted " in accordance with the numerical significance of the digit column with which each one is associated, and the sum of the outputs of the current generators is applied to the deflector plates 15 to position the beam. A quantizing control is again obtained from apertures 26. Specifications 836,234, 836,236 and 836,237 are referred to.</p> |
