Patent GB-620497-A (GB)
Title: Improvements in or relating to the transmission and reception of telegraphic signals
IPC: H03K11/00
Filed: 1946-07-11
Abstract: 620,497. Code telegraphy. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. July 11, 1946, No. 20741. Convention date, June 24, 1943. [Class 40 (iii)] In a telegraph system in which the beginning and end of each signal element are denoted by boundary indications of suitable wave form, whose duration is short in comparison with the duration of the signal element, the indication denoting the beginning of the signal element differs in aggregate duration from the indication denoting the end of the element. The beginning and end of a signal element may be indicated by different numbers of pulses of similar or identical wave form. Fig. 2 shows a circuit arrangement for generating two impulses at the beginning and one impulse at the end of a code element. The movement of the arm 1 to the left-hand position charges condensers 6, 11 simultaneously through resistances 7, 12 respectively, and the time constants of the circuits 6, 7 and 11, 12 are different so that the tubes 8, 13 attain their striking voltages sequentially to produce at a resistance 9 pulses 10, 14, corresponding to a voltage surge and the discharge of the condensers. The pulse at the end of the code element is produced by moving the arm 1 to the right-hand position in which a condenser 15 is charged through a resistance 16, and discharged by the operation of the valve 16<1> to produce an impulse 17. The impulses are fed to a transmitter 3, 4 by a resistance 9 in the cathode circuit of the tubes 8, 13, 16<1>. In a modification, Fig. 4 (not shown), the signals are fed to the transmitter by separate resistances in the cathode lead of the three tubes with associated decoupling resistances. The tubes 8, 13, 16<1> may be replaced by neon tubes. Receiving arrangements. The signals after detection and demodulation are fed to a valve 107 and to a valve 106 normally conductive and associated with a valve 105 normally non- conducting. The valve 107 is biassed negatively by a battery 111 so that it is made conductive by the integrated effect of two or more successive impulses. When the valve 107 becomes conducting a voltage drop occurring across a resistance 112 renders the valve 106 non-conductive. The valve 105 then conducts and at a resistance 113 applies an impulse to the receiving apparatus 104. The reception of a single impulse at the end of a signal element makes valve 106 conductive, which cuts off the valve 105 and terminates the impulse to the receiver 104. A device 102 may incorporate an amplitude limiter or a circuit arrangement, Fig. 6 (not shown), in which the received impulses operate a generator to produce impulses of constant amplitude which are fed to the circuit indicated at 103 in Fig. 5. The Specification as open to inspection under Sect. 91 states that the transmitting arrangement may be used to transmit code elements (dots and dashes) differentiated by the number of impulses at the commencement of the element, with or without an impulse denoting the end of the code element. This subjectmatter does not appear in the Specification as accepted.