GB555656A - Modulation of cathode ray device - Google Patents

Abstract

555,656. Cathode-ray tubes. STANDARD TELEPHONES & CABLES, Ltd. May 1, 1942, No. 5890. Convention date, Feb. 14, 1941. [Classes 39 (i) and 40 (iii)] In facsimile printing apparatus using a cathode ray tube 10 a flat beam from a cathode 11 after passing through a diaphragm 12 and accelerator 14 is deflected electromagnetically or by plates 15 over a number of discontinuous loops 18 carried on a rod 23 of insulating material ; the inner sides of the loops are within the tube 10 but their outer ends 25 are outside and an electrosensitive tape 35 passes over one set of these ends 25, an electrode 37 bearing on the tape opposite the ends. The impact of the beam on the loops 18 causes secondary emission, which is collected either by an auxiliary electrode 19 or by a conductor 27 housed in a recess 28 in the rod 23. The auxiliary electrode may be a plate or as shown is a carbon coating on the tube ; it is connected through a biasing source 45 to a signal receiving circuit comprising a resistance 51, an amplifier 47 and a resistance 46. The variation of potential of the auxiliary electrode corresponding to the received signal results in variation of flow of the secondary emission ; with no signal current all the secondaries emitted are collected by the electrode 19 but when a signal is impressed on the impedance 51 and the potential of the auxiliary electrode is sufficiently low all primary electron flow is to the output circuit and a signal is received on the tape. This is moistened with a suitable electrolyte. The spaces between the loops on the rod 23 may carry fluorescent material to enable the working to be observed. The accelerator electrode 14 is at the same potential as the coating 19, which may be divided into two or more sections. In a modified system of working, flow to the electrode 37 may be arranged when no signal current is applied to the impedance 37, the flow stopping as a signal is received.