Patent GB-782408-A (GB)
Title: Data processing system
IPC: G06K7/10
Filed: 1956-05-04
Abstract: 782,408. Statistical apparatus. STANDARD TELEPHONES & CABLES, Ltd. May 4, 1956 [May 10, 1955], No. 13828/56. Class 106 (1). Data represented by marks arranged in groups on a record card or strip, index marks being associated with each group of data marks, is scanned by a television-type flying spot scanner which repeatedly scans the record in a succession of lines so close to each other that each index mark is scanned by at least two successive lines each scanning producing a series of information bits which is repeated periodically, a different group of information bits being extracted after a given number of repetitions and sent to a utilization device, e.g.' a teleprinter. The groups may represent characters such as a letter or a numeral. The record 10, Fig. 1, may consist of a black and white photographic record of which each frame may consist, as shown in Fig. 2, of a picture 15 and a data area 16 recorded in the form of a five-position binary code of black dots, each row representing a character. For each row there is a black index dot 19 which is placed a little above the line of the data marka. In the flying spot scanner the film 10 is stationary and the frame shown in Fig. 2 is scanned from top to bottom in successive horizontal sweep lines 20, Fig. 3, as in the usual television raster. A different character is extracted after a given number of frame scans and printed, the process being continued until all the encoded characters in the frame have been printed by the teleprinter. The flying spot scanner comprises a cathode-ray tube 21 controlled by a synchronizing pulse generator 22. A photomultiplier tube 25 converts the data scanned into a video signal which is fed to a monitor television receiving tube 26 to produce on its screen a visual image of the recorded data. The normal scanning rate is 30 frames per second so that to obtain a data transmitting rate suitable for the teleprinter, i.e. about 5 characters per second, it is necessary to extract a character every six frames. For this purpose an index pulse, derived from the index mark, is used to control the opening of a character feeding gate which selects an encoded character to operate the teleprinter. One line is examined in each frame to determine if an index mark is present, the lines being examined in turn until a mark is found. The character gate is opened by this signal and the character is printed. After this, for the next five frames, during which the next five lines are examined, the character gate is blocked so that the same character is not printed twice. Six lines corresponds approximately to the spacing between rows of data. Upon examination of the sixth line a new index mark is found which again opens the character gate. Examination of succeeding lines in succeeding frame scans.-The timing of this operation is produced by passing the synchronizing pulses from generator 22 to a frequency divider 29. Each frame is assumed to consist of 525 horizontal scanning lines and divider 29 divides by 526, i.e. it produces an output every frame, plus one line. The output is passed to a gate pulse generator 30 through switch 31 or through another divider 32. This divider divides by two so that when switch 31 is open the rate of read-out is halved. Normally switch 31 is closed. The output from the gating pulse generator 30 and a pulse from synchronizing pulse generator coincide in circuit 33 to produce a pulse corresponding to a given point on those horizontal sweep lines (one in every 526) with which it coincides. This pulse is delayed in time in circuits 34, 35 so as to coincide with the position of the timing mark in the horizontal line and is applied to gates 36, 37 called " black " and " white " index gates. The video signal from the photo-multiplier is also applied to these gates through amplifier-limiter 38 producing a rectangular pulse, the signal to gate 37 being inverted in inverter 39. When an index pulse from amplifier-limiter 38 coincides with a delayed pulse from differentiator 35 there is an output from black index gate 36. This output causes printing of the character but since the same index mark is crossed by about three horizontal scanning lines, the same character would be printed three times if the gate signal alone caused printing. It is therefore necessary to prevent the output signal from the black gate from operating the character after it has once caused the character to be printed. Preventing second operation of the character gate.-The output from the black gate 36 is passed to one input of a bistable multivibrator 40 to trip it into one of its two conditions and the output of the white index gate 37 is passed to the other input to trip it to the second stable state. When the index mark is first found, the black index gate opens and trips the multivibrator from the second to the first state. This produces a change in the output voltage fed to a differentiating circuit 41 which produces in turn an output pulse to cause the character gate to open so as to print the character. In the next two examining sweeps (i.e. 526 and 1052 horizontal lines later) the index mark is found and the black index gate again passes a pulse to the multivibrator which, being in the first state, remains unchanged. In the fourth horizontal sweep there is a negative signal sent to the black gate since the scan has passed over the index mark so that this gate produces no further output but the inverter produces a positive signal and passes it to the white index gate, the output from which re-sets the multivibrator, ready for the next index mark to be found. Operation of the character gate.-The output from differentiator 41 is then passed through a number of delay devices 45 so as to produce a number of differently delayed pulses each of which coincides with the scanning of one of the data bits forming a character not in the same line as the index mark, but in the line following. The delayed pulses are passed through differentiating circuits 46 and applied to character gates 48 one for each data position. The video signal is also applied to these gates and the output pulses from these gates are passed through stretchers 50 to relays 51 preparing the teleprinter to print the character. A printing signal is obtained by delaying one of the gating pulses from differentiator 46, this pulse when applied to the teleprinter serving to print the character set up. Another arrangement is described for scanning a record as in Fig. 5 which consists merely of three columns G, H and I, each having a column of index marks and four data positions for each row. The reading is effected column by column, for example column G is read from top to bottom, the row 54 bearing a special signal to cause the reading to start at the top of column H. Row 54 of column H directs the reading to the top of column I and row 54 of this column stops the reading. The scanning is effected by a flying spot as before which scans the whole record at a high speed, the synchronizing pulses being passed to a divider as before for the control of the character gate. In this case the divider divides by 525 instead of 526 as above, but the gate generator 30 is connected to a gate interposed between the synchronizing pulse generator 22 and the divider which is effective to block one of the pulses so that the divider, in fact, gives an output every 526 pulses as before. This output is fed through a variable delay device to a monostable multivibrator which produces an output pulse whose duration may be large enough to cover the time during which a horizontal sweep moves across an entire character. This pulse 68 (Fig. 5), is applied with the video signal to a gate, the pulse beginning a short while before the index mark of the character is read and ends before the next column is reached. When an index mark is scanned during this pulse, it passes a pulse through the gate and trips a bistable multivibrator controlling the character gate as before so that the character is printed. At the bottom of column G the printer emits a pulse which operates a step switch connected to govern the delay produced in the variable delay device. This causes the gating pulse to start just before the scanning spot reaches the index mark of column H and to end before column I.