Patent GB-882428-A (GB)
Title: Communications system for transmitting and recording graphic information
IPC: H04N1/23
Filed: 1958-12-01
Abstract: 882,428. Copying telegraphy. FAXIMILE Inc. Dec. 1, 1958 [Feb. 20, 1958], No. 38264/58. Class 40(3). Copying telegraphy. Video signals corresponding to the point-by-point scanning of a transverse line of copy are received at 26 from a transmitter T and applied to a plurality of gate stages 36 which are opened in turn by pulses from a distributer system 56, 58, 68, 70, 72 (see below) so as to produce signal samples corresponding to successive points along the line, the samples being stretched in circuits 80 for a duration equal to the line scanning time and applied through amplifiers 82 to control the simultaneous recording of the line by multi-styli printer 76. In the example described, each line is considered to comprise 100 points, there being provided 100 gates 36 and distributer system 72 being controlled to produce a sequence of 100 pulses during the scanning of each line. Each line of video signal is preceded by a synchronising pulse in the blacker-than-black direction and this is separated by circuit 40 and employed to trigger on a pulse generator 42. The resulting pulses step a multi-anode counting tube 58 having ten anodes and this in turn steps a second similar tube 56 after each ten pulses. At the completion of 100 pulses a stop circuit 52 terminates the operation of generator 42. To allow for circuit delays, the trigger pulses for tube 56 are taken from the ninth anode via an adjustable delay circuit 53. For similar reasons, stop circuit 52 is operated from the tenth anode of tube 56 and the seventh anode of tube 58, so as to operate at the ninety-seventh pulse, and includes an adjustable delay circuit. A phasing circuit 46, which is triggered by the synchronising pulses, so as to reset tubes 56 and 58 on the first anode before each count. The pulses from the multi-anode tubes 56 and 58 are applied through coupling circuits 68 and 70 to a distributer resistor matrix 72 and result in the application of pulses in turn to gates 36. The invention is described as applied to signals originating from black and white copy, a trigger circuit 30 in circuit 26 being employed to restrict the signal to two possible levels. Each stretching circuit 80 comprises a circuit, Fig. 10 (not shown), in which an input signal sample pulse discharges a capacitor and cuts off an associated transistor generating an output pulse for the recharge time. The invention is primarily intended for use with electrolytic recording, although difference is made to non-electrolytic recording. A photo-electric transmitter for use with the invention is described with reference to Figs. 2 and 3 (not shown) and comprises optical means for projecting a line image from a copy web on to a slit scanned by a radially apertured disc. The slits in the disc are spaced by a distance sufficient to cut off the image at the end of each line to introduce a blacker-than-black synchronising pulse. Distributer system, Figs. 7a, 7b, 8. Pulses from generator 42, Fig. 1, appear on lead 47 and trigger multi-vibrator 62 which applies potentials to grid electrodes of multi-anode counting tube 230 and is effective to step the discharge from anode to anode to produce pulses in turns on leads b1 to b10. A connection from the ninth anode is taken via lead 61 to trigger multi-vibrator 60 which controls a second counting tube 228 in a similar manner. The input to the multivibrator as applied via an adjustable delay circuit 53 formed of a single pulse multivibrator which permits the stepping of the two tubes 230 and 234 to be properly phased despite inherent circuit delays. Tube 224 steps at one-tenth the rate of tube 230 and produces pulses on leads a1 to a10. Leads b1 to b10 and al to a10 are connected through individual transistor coupling stages 70 and 68, Fig. 8, to the inputs of resistor matrix 72. The pulses from the two sets of leads are added in the matrix and result in double amplitude pulses appearing in turn at 100 output leads 73. Connections from leads a10 and b7 are taken to the input of the stop circuit 52, Fig. 7b, and result in a double amplitude pulse at count 97 which is selected by biased rectifier 266 and applied to stop the operation of generator 42, Fig. 1, over lead 44. The circuit includes an adjustable delay circuit 274, 275 formed of a multivibrator which is adjusted, having regard to inherent circuit delays, so that the generator is triggered off after exactly 100 pulses. A blocking oscillator 232 which is triggered by a synchronising pulse before each count applies potentials to the spade electrodes of tubes 228 and 230 to set the discharge at the first anode. Specification 637,088 is referred to.