Patent GB-774292-A (GB)
Title: Improvements in and relating to electrical communication systems and apparatus
Inventor: DAIN GORDON TAYLOR
IPC: H04L12/00
Filed: 1954-03-03
Abstract: 774,292. Telegraph exchange systems. BRITISH TELECOMMUNICATIONS RESEARCH, Ltd. Feb. 17, 1955 [March 3, 1954], No. 6229/54. Class 40 (3). A telegraph switching system employs arrangements for the received characters, represented by code combination of elements, to be advanced progressively through the different positions of a multiposition storage device, each position of which includes a two-position register for each element of the character, and is such that in a group of one or more storage positions the registers, in addition to being connected to those of the succeeding storage position, are also connected to responding equipment arranged to effect specific switching operations if the registers in those storage positions are set to store predetermined characters. As shown, the start and code elements are applied by a distributer D1 to a first set of cold-cathode tubes A1 ... A6, the conditions of which are transferred to the tubes B1 ... B6 by a pulse P generated by the distributer D1 during the stop element of the received signal. A startstop distributer D2 set into operation by D1, or if a start element is registered in the start tube of the bank N, has a cycle of operation with a period less than that of D1 and provides a pulse Q which transfers the pattern along the groups B, C ... N of the storage tubes and removes the pattern on the group N1 ... N6. The distributer D2 also passes the pattern transferred to the tubes N1 ... N6 to the outgoing line. The operation of the tubes A1 ... A6 by the incoming signal elements may be such that pulses applied by the distributer D1 to capacitors C1 ... C6 are suppressed by the marking elements so that spaces selectively light up the tubes A1 ... A6. The operative tubes provide current through associated resistors R2 to charge capacitors C7 in the inputs of the tubes B1 ... B6. The anode circuits of the tubes B1 ... B6 are simultaneously opened by contacts X1, and pulses P, applied simultaneously, operate those tubes primed by the tubes A1 ... A6 which are lighted. The anode circuits of the groups of tubes C ... N are simultaneously opened by contacts X2, and pulses Q applied simultaneously to the tubes effect the transference of the pattern from one group to the next. The pulses from the groups E, F, G are applied to a coincidence circuit, Fig. 4, so that for the predetermined characters the cathodes of the tubes E, F, G which should be conducting are connected to the input of a tube V3, whilst the cathodes of the remaining or complementary tubes, which should be non-conducting, are connected via oppositely poled rectifiers to the input of a tube V2. When the predetermined code appears on the groups E, F, G, and the pulse Q is applied RB to the grids of the tubes V2, V3, relay - is 1 RA operated and relay - remains unoperated so 1 that the closing of contact RB1 applies a potential to a switching lead Z. To prevent the switching control from being operated by sequences of characters which may occur in a message, the switching combination of characters is combined with an enabling or conditioning code applied through groups C, D to a discriminating circuit ECE so that the switching code is operative solely when it is followed by the enabling code. The switching code may effect connection to a desired station or alternatively to a selected main station and there be repeated to extend the call to a sub-centre at which the repetition of the switching code extends the connection to the desired station. The signal impulses passed by D2 to the line may also be passed to groups O, P so that a predetermined combination of characters operates the discriminating circuit CCC to generate a clearing signal, this combination being preceded, if desired, by a conditioning code to prevent the operation of the circuit CCC by the occurrence of the predetermined characters in the actual message.