Patent GB-732346-A (GB)
Title: Improvements in or relating to electrical decoding circuits
Inventor: WRIGHT ESMOND PHILIP GOODWIN
IPC: H04L17/30
Filed: 1949-12-02
Abstract: 732,346. Digital electric calculating apparatus. STANDARD TELEPHONES & CABLES, Ltd. Nov. 2, 1950 [Dec. 2, 1949], No. 26745/50. Divided out of 732,341. Class 106 (1). [Also in Group XXXVIII] Apparatus for de-coding a multi-element, two-condition code comprises n two-condition switching devices adapted to respond respectively to successive elements of the code, beginning with the first permutable element, means consisting of 2n multi-position devices for converting the remaining permutable elements into a decimal number, these devices being individually selectable by the characteristic settings of the two-condition switching devices, and means for setting a selected multiposition device to a position characteristic of the value of the decimal number. In the described embodiment the timing of the circuit is controlled by a 10 kc./sec. pulse source emitting simultaneously positive and negative P pulses, Fig. 1. The positive pulses pass via a ¸ 3 counter of the type described in Specification 677,872, using three cold-cathode gas discharge tubes TA1 ... TA3, and a ¸ 10 counter of the type described in Specification 692,415 comprising a multi-cathode tube TB, to a ¸ 7 counter or character distributer TC. This last, is also.a multi-cathode tube, each of its seven. outputs occurring at the beginning of one signal element of a received character ; in combination. with the tube TB any. required timing can be obtained. The incoming signals, in telegraphic code appear in the form of .positive potentials on separate space " and " mark " lines, being derived from a tape reader in known manner. By means of coincidence gates controlled by-the timing circuit (Fig. 4, not, shown), the first permutable elements is registered on a trigger pair of cold-cathode gas discharge tubes AS, AM and the second permutable element on a trigger pair BS, BM. The positive potentials appearing at the cathode of the conducting. tube in each trigger pair AS, AM, BS, BM, are applied to resolving circuits such as that shown in Fig. 5 which is operative only when both " space " tubes AS, BS are conducting. Under control of the timing circuit (gates TC3, TB9, TA3F) the potential of the trigger electrode of an associated cold-cathode tube TGRA, Fig. 1 (and Fig. 6, not shown), is brought to a condition to cause the tube to fire when the next - pulse appears at its cathode. This, in turn, causes a multi-cathode. tube RA to step to the one " position. All elements of an incoming. signal are applied to a third trigger pair of coldcathode tubes S, M, Fig. 1, but the trigger pair exercises no control until the registration of the third permutable element which, if a "space," causes positive potential at the cathode lead Sc, Fig. 1. and 5, and, in coincidence with timing potentials TC4, TB7, TA3F (and also potentials on ASc, BSc, assuming that the first two permutable elements were both " space ") the tube TGRA is again brought into condition to be fired by a - P pulse, and the tube RA is. stepped to the " two " position. If the fourth; permutable element is a " space," timing voltages TB7, TB9 cause the tube TGRA to fire twice, giving two steps to the tube RA ; if the fifth permutable element, is a " space " four steps result at times TB7, TB9, TB1 and TB3. When. a " mark " appears in any of the. last three permutable elements no stepping of the tube RA, RB, RC or RD selected by the first. two permutable elements occurs. Thus the discharge in any of the multi-cathode tubes RA, RA, RB, RC, RD can take up any one of eight positions giving 32 possibilities, sufficient to interpret the code used. Specification 636,700, [Group XL,(c.)], also is referred to.