Patent GB-619785-A (GB)
Title: Improvements in and relating to multi-channel signalling systems
IPC: H04J3/04
Filed: 1946-12-20
Abstract: 619,785. Thermionic distributers. GENERAL ELECTRIC CO., Ltd., and LEVY, M. M. Dec. 20, 1946, No. 37501. [Class 40 (iii)] [Also in Groups XL (a) and XL (c)] In a multi-channel pulse signalling system the different channels are served bv a number of electronic distributers, each having a plurality of control electrodes associated with a corresponding number of channels and a rotating electron beam for routing the signals via common anodes to a distributermodulator which converts the signal voltage variations into pulse-time or pulse - width modulations. As shown in Fig. 1, two 50 kc. sine waves 90 degrees out of phase are produced by a master generator A and selective amplifier B and are applied to the deflecting coils MC<1> and MC2 of a distributer-modulator M, Fig. 3, the deflecting electrodes MD<1>, MD3, MD <5> ... MD<23> of which are connected to distributers D<1> ... D<6> which collect the signals from the different channels C<1>, C3 ... C<119>. The distributer-modulator is provided with an inner electrode ME co-operating with the electrodes MD to deflect the cathode ray radially inwards and outwards over slots MS in a plate MP, thus retarding or accelerating the instant at which a pulse is generated at the anode MA, proportionally to the signal variations applied to the deflecting electrodes. Once in every revolution the cathode beam strikes an electrode MG and generates a pulse stream of 50 kc. which is fed to a multi-vibrator H and selective amplifier J. An output, of two 5 kc. sine waves 90 degrees out of phase, is thereby produced to rotate the cathode beams of the distributers D<1> ... D<6>. Each distributer comprises two anodes DAA and DAB, Fig. 2, a screen grid DS, an elongated cathode DE, and ten control grids DG, the arrangement being such that a beam of electrons extending radially in opposite directions rotates about the cathode. Fig. 1 shows the arrangement for the odd numbered channels C<1> ... C<119> of a 120 channel system, a similar arrangement being provided for the even numbered channels. In operation, the signal voltages present on the control electrodes C<1>, C<3> ... C<119>, are successively picked up by the distributers D<1> . . . D<6> and are applied by means of the anodes DAA<1>, DAB<1> ... to the appropriate electrodes MD<1> ... MD<23> of the distributer modulator. As the cathode beam in the modulator comes under the influence of the electrodes MDl ... MD<23> it is deflected radially and causes modulated pulses at the anode MA. The pulses may be modulated in time or duration according to the type of slot employed in the plate MP, and are fed to an amplifier F and transmitter G. As shown in Fig. 2, each distributer D<1> ... D<6> has a screen grid DS comprising grid portions opposite the control electrodes DG separated by plate portions which serve to intercept stray electrons such as e<1>. Electrons as indicated at e<2> are prevented from causing cross talk by means of screening electrodes DF, of which. alternate ones are connected together. The two sets of electrodes DF are fed with oscillations 180 degrees out of phase, and arranged so that interference from electrodes adjacent the effective electrode is prevented. Radial screens extending towards the cathode may also be provided.