Patent GB-657751-A (GB)
Title: Improvements relating to code telegraphy
IPC: H03M13/51
Filed: 1947-09-22
Abstract: 657,751. Type-printing telegraphy. CABLE & WIRELESS, Ltd., and HIGGITT, H. V. Sept. 22, 1947, No. 25759. [Class 40 (iii)] In a telegraph system in which a primary equal-length code is converted into a longer equal-length code having a fixed ratio of marking and spacing elements in all the signals, the signals in the primary code are divided into two groups of elements, and, except for a small number of signals, the first group is identically transmitted as the first group of the equal-ratio code, whilst the second group of each signal in the primary code is modified by the transmitting apparatus into a group in the equal ratio code determined in its permutation of marking and spacing elements by the number of elements of one kind in the first group and the permutation of the elements in the second group of the primary code signal. The primary five-unit code which is to be converted into a sevenunit equal-ratio code having 3 marks and 4 spaces is divided into series of signals in which the second group comprises the possible permutations of a mark (M) and a space (S), i.e. MM, SM, MS, SS, and the first group of the respective series includes three marks, two marks, one mark and no marks, as exemplified by Table I included in the Specification. Except in the case of the fiveunit signal beginning MMM, the first three elements of the seven-unit equal ratio code signals are identical with the first group of the series into which the five-unit code is subdivided, and the seven-unit code is completed by second groups of four elements which include one, two or three marking impulses, the positional occurrence of the marking pulse or pulses in the second, i.e. four-unit group, being determined by the MM, SM, MS, SS arrangement occurring in the second group of the five-unit code signal. In the case of the five-unit signals beginning MMM, the first three elements of the seven-unit code are arranged to be MSS or SSM according to the termination of the five-unit signal in a mark or a space element respectively. Transmitting arrangement, Fig. 1. Peckers Pa ... Pe controlled by a tape perforated according to the five-unit code selectively energize magnets A ... E which, on operation, lock-up over springs al ... e1 and a ring 7 associated with a brush Br2. Normally the first three elements are applied unchanged by operated springs a7, b7, c7 to transmitting segments S1, S2, S3 engaged by a brush Br1 connected to the outgoing line L. If the first three elements of a signal are MMM and the fifth element is also M, a circuit is completed over operated springs a6, b6, c6, e2 and conductor 12 to operate in series the relays M3, M2 which at contacts 10 open the connection from the springs b7, c7 to the segments S2, S3 and therefore convert MMM into MSS. If the fiveunit signal beginning with MMM ends in S, a circuit is completed over a6, b6, c6, released contact c3 and conductor 14 to operate in series the relays M1, M2 so that the elements MMM are converted to SSM. The combinations MM, SM, MS, SS forming the second group of the primary five-unit signals operate respectively the relays F, G, H, K, the operation, for example, of relays D, E by fourth and fifth marking elements closing a circuit from battery over operated springs e2, d2 to the winding of relay F. In the second series, the relays A, B, C controlled by the first three units are effective to add a second mark immediately following the mark applied by the group MM, SM, MS, SS. For example, the group MS adds a mark in the third position of the four-unit group of the seven-unit signal, and the group MSS of the five-unit signal by operation of relay A completes a circuit from battery 27, spring b3, spring c2, conductor 30, operated spring h1, since relay H is operated by the combination MS, to segment S7 so that the combination MSSMS is converted to MSSSSMM. When the first three units of the five-unit signal are all spacing -SSS-, i.e. none of the relays A, B, C is operated, and where the group SSS is followed by MM, a circuit is completed from battery over released springs a5, b5, c5, conductor 35, operated contact f2 to segment S6. Another circuit is completed from battery 27, released spring b2 to wire 30 and over operated spring f1 to the segment S5 so that the five-unit signal combination SSSMM is converted to SSSMMMS, the signal SSSSM to SSSSMMM, and so on. The combination MMM is converted to MSS or SSM for five-unit signals ending in M or S respectively, and for the second group MM in this case, since relays A, B, C are all operated and relay F is also operated, battery is connected over operated springs a4, b4, c4, f2 to segment S6 so that the five-unit signal MMMMM is converted to MSSMSMS. The five-unit signal MMMMS is converted to SSMMSMS, and the signals MMMSM and MMMSS are converted to MSSSMSM and SSMSMSM respectively. Three other signals SMSMSMS, SMSSMSM and MMMSSSS which may be formed in the sevenunit equal-ratio code may be transmitted by a manually-operated member connecting battery selectively to the segments S1 ... S7. Receiving arrangement, Fig. 2. The received signals are passed via segments RS1 ... RS7 to relays N, O, P, Q, R, S, T which, on operation, lock up over a continuous ring 41 and a brush Br2. When any three relays are operated a circuit is completed for a test relay TR and when brush Br3 contacts a segment 55, battery is applied over spring tr1 and contact 53 to conductors 56, 66. If more or less than three marks are received, test relay TR does not operate and battery is applied by a brush Br3 and released contact 51 to a line 52 leading to an error-indicating apparatus. Alternatively battery can be connected over line 93 so that a mark is transmitted from the third segment of the distributer to conductor 99 and the line L leading to a teleprinter on which this signal records a space. Assuming the signal has been received correctly, relay TR operates and battery is connected to conductors 56, 66. Except in the cases when the four final elements of the received signal are MSMS or SMSM, the first three elements of the received signal correspond identically with the first three elements of the primary five-unit code and the signal elements received by relays N, O, P are passed over springs n4, o5, p5 and released springs ma, mb, mc of relays Ma, Mb, Mc to segments 59, 60, 61 connected subsequently by brush Br4, line 99, released spring cor2 of relay COR and line L leading to a teleprinter or to a land line. When the four final elements are MSMS or SMSM-i.e. relays Q and S or R and T are energized, a circuit is completed from battery 54 over spring tr1, contact 53, conductor 66 and appropriate springs of relays Q, R, S, T, to energize relays Ma, Mb, Me in parallel and at the three contacts 65 engaged by operated springs ma, mb, mc battery from the conductor 56 is applied to segments 59, 60, 61 of the retransmitting distributer. The four-element combinations forming the second group of the seven-unit signal control the relays Q, R, S, T, whose springs q8, q9, r8, r9, s7, s8 and t6, t7 are interconnected in such a way that relays W, X, Y, Z are operated according to the sequential position of the mark M or the first mark of the combinations MM, or MMM. For example, in the case of the three-mark group MMSM, relays Q, R and T are energized and a circuit is completed from battery 54, spring tr1, contact 53, conductors 56, and 69, released spring s7, operated spring t7 through winding of relay Z. The operating circuits of the relays W, X, Z are, in this case, broken by springs t6, q8 and a8 respectively. The operation of the relays W, X, Y, Z result in applying respectively signals MM, SM, MS and SS to the fourth and fifth segments 62, 63 of the distributer. For example, the operation of the relay W applies battery over released spring y, operated spring w2 and contact 84 engaged by released spring mx to segment 63 and over operated spring w1 to the segment 62. In the cases of the second group of code elements MSMS and SMSM associated with the five-unit signals beginning MMM, relays Q and S or R and T are operated and result in the energization of W and Y, or X and Z, respectively. The energization of W and Y applies a mark to the fourth segment 62, but since the relay N is energized in this case, a circuit is completed over conductor 66, t4, s5, r6, q6, contact 86 engaged by spring n3 to relay Mx, so that a mark is applied to the segment 63. In the second case, i.e. for signals having SMSM as the second group, and the first group as SSM, relays R, T, X and Z are operated. Relay Mx is not operated in this case, and battery is not applied to either of the segments 62, 63. The three additional signals in the seven-unit code may be used for signalling purposes, and one or more of these signals may be utilized to close the circuit of a relay COR operating, at contact cor1, a bell 98, and at spring cor2 applying a stop (marking) element to the outgoing connection L. An additional cut-off relay COR2 may be operated by the third of the additional seven-unit signals. Modified transmitting and receiving arrangements. A transmitter, Fig. 3 (not shown) for converting a six-unit code into an equal-ratio eight-unit code and an associated receiver, Fig. 4 (not shown), operate generally as described for the arrangements shown in Figs. 1, 2. The operating circuits at the transmitter and receiver are modified and somewhat simplified by the use of rectifiers in a number of the battery connections to the segments and to the springs of the relays. The Specification refers briefly to the use of thermionic valves in place of contact-making relays.