GB637820A - Pulse code signalling systems - Google Patents

Abstract

637,820. Cathode-ray tubes. WESTERN ELECTRIC CO., Inc. Aug. 8, 1947, No. 22025. Convention date, March 22, 1946. [Class 39 (i)] [Also in Groups XXXIX and XL (c)] A varying voltage representative of a telephonic or other signal is sampled at recurrent intervals and the sample voltages used to deflect a cathode-ray beam along one co-ordinate. Between consecutive samples, the beam is deflected along the other co-ordinate to traverse a coding element producing a group of pulses representing the voltage of the preceding sample. The coding element may be arranged to produce groups of pulses in accordance with the binary scale. The sample voltages are fed through a. cathode follower 56 and amplifier 58 to the vertical deflecting plates of the C.R. tube 60. Between the taking of consecutive voltages, the C.R. beam is given a horizontal sweep by a saw-tooth voltage generated across the condenser 12 of the relaxation and fed to the C.R. tube through a cathode follower 30. The fluorescent screen of the tube is covered on the outside or inside by a mask, perforated in the manner shown in Fig. 2 to represent consecutive numbers in the binary scale. As the beam passes a perforation, light passes through lens 65 to a photo-electric cell 66, and gives rise to a pulse which is amplified at 69 and transmitted by the radio or like transmitter 71. Instead of a fluorescent screen the C.R. tube may have a metallic target electrode located behind a perforated mask, and the output may be taken across a resistor connected between the target and earth, or between the mask and earth (Fig. 5, not shown). Specifications 630,094 and 637,848, [both in Group XL (c)], are referred to.