Patent GB-926731-A (GB)
Title: Improvements in or relating to systems for recording characters on light sensitive recording surfaces
Inventor: HUNTLEY KEITH GORDON
IPC: G06K15/12
Filed: 1958-04-03
Abstract: 926,731. Cathode-ray tube circuits. RANK PRECISION INDUSTRIES Ltd. March 23, 1959 [April 3, 1958 (2)], Nos. 10763/58 and 10764/58. Class 40 (7). [Also in Group XX] In a printer of alpha-numeric and other symbols, which may form the decoded output of a digital machine, wherein the output is visually displayed and optically projected upon a moving light-sensitive recording surface, a standard image comprising fixed characters such as a photographic image of an insurance form, is projected on to the moving recording surface simultaneously with variable characters, such as the name of the insured, which are generated in response to input signals and projected on to the recording surface in appropriate relation to the fixed characters, and means is provided for selecting for projection a chosen one from a store of standard images. As described with reference to Figs. 1 and 2, the printer logics are concerned with obtaining slant-free lines with flush left or indented margins and with recording the variable characters at any chosen location (" address ") on the recording surface, while the additional feature of the selection of a chosen fixed image in addition to the variable characters is described only in the Fig. 4 embodiment. Slant-free line production.-Characters are formed by signals generated at 1 by dot synthesis under instructions from a character selection matrix 5 and timed by a sequence pulse generator 7 and the X and Y output waveforms are applied through " or " gates 27, 28 to the X and Y plates of a cathode-ray tube 2 to display the characters which are projected by a lens 8 on to a xerographic drum 9 from which a developed positive is transferred on to a paper strip. The sequential pulse generator is operated through a bi-stable 18 by a " dot clock " 17 which may be a multivibrator and at each dot generated a pulse is passed via " and " gates 20 or 21 over " or " gate 24 to " and " gate 25 to lift a clamp voltage from the control grid of the display tube to increase the spot brightness on emergence of the Y waveform, a noise limiter 42 being provided. Either the first or second pulse from the pulse generator 7 is applied over " or " gate 29 to provide a switching pulse to the character selection matrix 5, set by code signals from a computer over lines 6, so that it instructs the character generator 1. When the pulse generator 7 resets itself after formation of a character, it emits a pulse which is fed to the horizontal display address register 10 which is a binary adder and to gate 34. The output from the register 10 is fed both (a) to a converter 31 which develops a voltage which is applied to the X-plates of the display tube to displace the beam horizontally, and (b) over " or " gate 35 to " and " gate 34, whereby a bi-stable 16 is caused to apply a set pulse to the pulse generator 7 in step with the dot clock 17 to trigger off another sequence. To ensure that successive characters are recorded on the drum 9 along a common generator, a rate signal is derived from a tachometer driven with the drum which controls a sawtooth voltage to be applied to the Y-plates of the display tube to compensate for the drum movement by vertical displacement of the character display. Two lines of characters may be displayed one above the other on the cathode-ray tube and a further stage 40 of the horizontal address register 10 is then effective to apply a vertical displacement voltage to the Y-plates to bring the two sets of characters in alignment in the recording made on the drum to produce a longer line. When the horizontal address register 10 has been filled and reset by the subsequent pulse so that all its stages are in the " 0 " position, there is no potential applied to " and " gate 34 via " or " gate 35 so that the reset pulse of the pulse generator 7 cannot operate bi-stable 16 indicating that a fresh line must be started. Connected to the drum 9 is a tachometer 12 or a photo-electric or magnetic analogue which emits pulses to feed a counter 13 and this when filled emits a line start signal via pulse shaping unit 36 over lines 15, 14 to operate the bi-stable 16 and adds one to the vertical address register or line counter 11. At the end of a page a photo-electric or magnetic sensing arrangement is operated to reset the horizontal and vertical address registers 10, 11 and the pulse counter 13. Address selection.-If it is desired to print at selected locations only on the sheet, horizontal and vertical address inputs 51, 53 (Fig. 2) are set, e.g. by orders in the code input, and pulses signifying that such settings are to be effected are applied over lines C, D to bi-stables 56, 59 which via " or " gate 57 inhibit the gate 54 and so prevent the sequential pulse generator from applying a switching pulse to the character selection matrix for character read out to the character generator. Character generation is thus inhibited until there is coincidence between the horizontal and vertical address set inputs and the horizontal and vertical address registers as detected by units 50, 52 to reset the bistables 56, 59 and uninhibit gate 54. Typically, the address input circuits involve a binary code decoder giving say 16 alternative outputs connected by plug boards to any chosen sixteen of a possible, say, 128 lines, each corresponding to an address position, said lines feeding into a seven output line binary encoder which is led to an address input register. Different addresses may be chosen by means of alternative plug boards selected by the instruction given to the machine. In the case of horizontal addresses the comparison circuit such as 50 may be omitted and the address input provided with a pulse output which may be applied directly to the display register 10, so deflecting the beam horizontally to the desired position. Due to the inertia of the drum 9 a similar arrangement cannot be applied for vertical addresses. As described, the rate of data input to the machine must be between the maximum permitted by the repetition rate of the character generator and the minimum ensuring display of a full line of characters. If instead the input is fed into a buffer store at a rate which is governed by an internal clock which far exceeds the character generation repetition rate read out from the store and printing may be effected independently of the input rate (within the limit of the store) and the variations in input rate above or below the limits referred to above have no effect. A machine incorporating all these features is illustrated in Fig. 4, in which gates 124, 125, 126, 158, 160, 179 are " or " gates, gate 121 is an " inhibit " gate, gate 149 and gate 151 are of special operation as described below, the single input gates are pulse-shaping devices, and the remaining gates are " and " gates. The dot clock 106 operates the sequential pulse generator 111 which is triggered for each pulse by a " sprocket " pulse over line 101 accompanying each 6-bit " word " read from a magnetic tape input. The tape runs continuously throughout a line of recording, unless arrested by a " vertical address " or a " stop " order, but stops at the end of a line, the code words representing the information for a line of recording being arranged in blocks separated by a space to allow for deceleration of the tape to rest and acceleration to operating speed on restarting. For restarting the tape after it has stopped at the end of a line or after a vertical address order, a " line start " signal is provided over line 147 from a photo-electric device operated from or a tachometer geared to the xetographic drum, while a manually controlled pulse is passed over line 155 to restart the tape after a " stop " order. The code " words " are themselves registered simultaneously as " arrays " over multiple line 100 in the pulse memories which comprises flip-flops and from which the " words " are called over multiple lines 112 by a pulse from the dot clock in coincidence with the sprocket pulse. A word, if character code, operates only the character code register 113 which through character selection matrix 114 and character generator 115 controlled by the pulse generator 111 supplies character-producing X- and Y-waveforms to amplifiers 118, 119 for the X- and Y-plate deflection voltages. As previously described with reference to Fig. 1, a sawtooth voltage is applied to the Y-plates from a drum-operated tachometer by generator 200 in time with a " line start " signal over line 147 to compensate for movement of the xerographic drum. If order code, which comprises two words if numerical data accompanies the order, is read from the buffer input, both the character code register 113 and the order decoder unit 122 are operated. All orders cause inhibition of gate 121 to prevent character display. A " blank " order is decoded by section 122g simply to inhibit character generation over " or " gate 160, bi-stable 161 and " or " gates 125, 126. The first words of the horizontal and vertical address orders are decoded by sections 122a, 122b respectively to effect inhibition of gate 121 over " or " gates 124, 125, 126 condition " and " gate 136, and apply potentials to " and " gates 131, 132 respectively, and when the second word of the code arrives at said gates in synchronism with a sprocket pulse over bi-stable 135, " and " gate 136 and bi-stable 137 which pulse also inhibits character generation over " or " gate 126, the horizontal and vertical address input decoders 129, 130 are operated in accordance with the instruction contained in the second word, and over plugboards 140 which if connected internally to all the output lines of the decoders on which signals are present operate address output encoders 141, 143. The encoded horizontal address instructions are applied to the horizontal address register which operates its analogue converter 138 to apply the required horizontal deflection voltage to the X- plates. 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