Patent GB-711901-A (GB)
Title: Improvements in or relating to electric telegraph systems
Inventor: WRIGHT ESMOND PHILIP GOODWIN
IPC: H03M5/00
Filed: 1950-08-25
Abstract: 711,901. Code telegraphy. STANDARD TELEPHONES & CABLES, Ltd. Aug. 17, 1951 [Aug. 25, 1950], No. 21042/50. Class 40 (3). [Also in Group XL(c)] In a circuit arrangement for translating a start-stop teleprinter code combination into an error-indicating code combination or vice versa the setting up of all circuit conditions for the examination of received combinations of one kind, and the translation of said combinations into those of the other kind is performed wholly by means of static electrical switches. Conversion from five-unit code to seven-unit error code.-The timing circuit for the examination and translation of the code combinations comprises three multi-cathode discharge tubes C1, C2, C3 fed with pulses P- at a frequency of 5 Kilocycles and associated with gating circuits G2, G3, G4 so that the tubes Cl, C2, C3 operate to count all the pulses, every tenth pulse and every hundredth pulse, as described in Specification 692,411. In the stop position of the circuit the tube SP of the flipflop F1 is fired and over a lead 204 tubes 1, 2, 5 of a space-counter chain R3 are fired to set up a pattern MMSMMSSM on the tubes 7 to 0. When the start element is received a gate G1 of the type disclosed in Specification 636,700, [Group XL(c)], is opened and start tube ST of the flip-flop F1 is operated so that pulses P- at the 5 Kilocycles frequency operate the timing circuit. At time 30, 50 ... 110 ms after the commencement of the start element, the reception of a space element is transferred through a gate G6 and a gate G7 to tube 6 of a register R1, operated as described in Specification 663,574, the pattern on which is stepped by pulses Ps at times 3, 23 ... 103ms so that at the end of 110 ms the code signal is set up on the tubes of the non-repeating chain R. Whilst the code combination is being set up on R1, the number of spacing elements is being determined by a space-counter R3 comprising a non-repeating chain in which tubes 1, 2, 5 are fired to form the initial pattern. At the timing instants 30, 50, 70, 90, 110 ms, a pulse is applied to gate G20 which opens on spacing elements received over line 205 to pass a pulse through gate G21 and a pulse shaper S3 to the chain R3 which moves the pattern one step to the right, and at times 40, '60, 80, 100, 120 ms a gate G24 is opened to allow the condition of the tube 0 to be repeated, or assumed, by tube 7, but this does not cause the pattern to be advanced. Assuming the code combination includes one space, the pattern on the tubes 7 ... 0 will be MMMSMMSS, and at the end of 120 ms the pattern will be SMMSMMSS. Tubes 0, 1 of R3 record two spaces which will be the correct prefix for a 5- unit code combination containing one space. At 121 ms gates G12, G10, Fig. 1, open so that the condition of the tube 0 of R3 is repeated to tube 1 of prefix register R2. At 122 ms gate G11 is opened to transfer the condition of tube 1 to tube 0, and at the same time a gate G27 is opened to step the pattern on R3 one position to the right so that the condition of tube 1 is transferred to tube 0 and the pattern on R3 is MMMMSMMS. At 123 ms, the gates G10, G12 are opened so that the condition of tube 0 of R3 is transferred to tube 1 of R2. Pulses at 124, 126, 136 ms clear the pattern off the tubes 7 ... 0 of R3, and this is restored at 138 ms by the operation of stop tube SP of the flip-flop P1. The pattern of the seven-unit signal is now stored on tubes 0, 1 of the prefix register R2 and on the code combination register R1. At the beginning of the next code combination at time 0, gate G13 opens to fire mark tube MO and to extinguish space tube SO, and at 0.2 ms gate G14 is opened if a potential exists on lead 202 to prefix tube 0 so that the space tube SO is again fired. At 1 ms gate G11 is opened and the pattern on R2 is stepped so that the second element of the prefix is on the tube O of R2. At time 2 ms gate G9 is opened to allow the condition of tube 2 of R1 to be transferred to R1 of the prefix register R2 and at time 3 ms gate G8 opens to allow pulse Ps to pass through S1 to move the pattern on R1 along one step so that the final four elements of the seven-unit combination are registered on tubes 2 to 5 of R1. At 20 ms, gate G13 opens to fire tube MO if the first element was a space, and 0.2 ms later G14 opens, and if the element on tube 0 is a space, the flip-flop F2 returns to space. The pattern is again stepped in two stages by pulses through S1, S2 and the remaining five elements are transmitted in sequence. Five-unit signals with four spacing elements.- In the case of a signal with four spaces, e.g. SSSSM, tubes 2, 3, 4, 5 of register R1 are fired, and the stepping of the pattern on the space counter R3 in combination with the change, if necessary, of tube 7 to accord with tube 0 results in the pattern MMSSMMSM. At time 101 ms gate G23 is open since tubes 4, 5 are both fired with the result that tube F is fired and tube N is extinguished. At times 121, 123 ms, the condition of tubes 0, 1 of space counter R3 is transferred to the prefix register R2 and this prefix is sent when the number of spacing elements in the original signal is none, four or five. The seven-unit signal setup on tubes 0 ... 6 is therefore MSSSSSM. At 40 ms F2 is biased to mark and at 40.2 ms is returned to space, but at 40.4 ms MO is again fired by a pulse through gates G17, G13 so that a mark is sent for the third element. The fifth element is also reversed at 80.4 ms so that the seven-unit combination sent out is MSMSMSM. Two other four-space code combinations are dealt with in a similar manner, the third and fifts elements appearing on the tubes 0 ... 6 being converted to marks. In the cases of the remaining four space combinations SSMSS and MSSSS, the same MS prefix is added and the third and fifth elements of the primary seven-unit combination are reversed giving MSMSSSS and MSSSMSS, both of which contain more than three spaces, so that space limiting is necessary. This is effected by a limiter comprising a three-step non-repeating chain C4. At 40.6 ms a gate G18 is opened and if F2 is on space, C4 is stepped to gap 2. If at 60.6 ms or at 80.6 ms, F2 is still on space, G4 is stepped to gap 3 and gate G19 is closed with the result that G15 is permanently closed and F2 is held on mark so that no further spacing e'ements can be transmitted and the sevenunit combinations become MSMSSMM and MSSSMMM. Conversion of the all-spacing signal.-In the case of the five-space combination, tubes 2 to 6 of register R1 are fired and the first four spaces cause the space counter to produce the pattern MMSSMMSM causing tube F of F3 to fire thereby closing gate G20 and opening gate G25. The closing of gate G20 prevents the fifth space element from stepping R3 and at 110 ms gates G25, G26 fire the all-space, all-mark tube A which extinguishes tube F and cuts off the reversing arrangement and space limiter of Fig. 2. The firing of the tube A opens gate G29 which provides output to G28 and via lead 207 to G8A. At 122, 124 ms the pattern on the space counter is advanced, the prefix MS is transferred to the register R2, the pattern on R3 becoming MMMMSSMM. At 125 ms gate G28 is opened and the condition of the tube 0 of R3 is transferred via connection 203 and gate G7 to tube 6 of R1. At 126 ms the gate G8A opens to allow a stepping pulse from Ps to pass via gate G8 to step the pattern on R1. Also at 126 ms the pattern on R3 is moved along one step and this process is repeated until the conditions of tubes 0 to 4 of R3 have been transferred to tubes 2 to 6 of R1, thus eradicating the five-space pattern originally stored. The combination stored on R1, R2 is MSMSSMM and this is the sevenunit combination allotted to the all space combination. Conversion of the all-marking signal.-In the case of the all-marking five-unit combination, the original pattern remains on the space counter R3 and at 111 ms the gate G22 is opened since tubes 1, 2 are fired and the all-space, all-mark tube A is fired. The subsequent operation is similar to that for the all-space signal, except that the combination transferred to R1, R2 and transmitted is MSSMMSM. Translating from error-code to five-unit code.- A synchronizing pulse coincident with the leading edge of the first element of the seven-unit combination opens gate G31 and fires start tube S1 so that the time circuit Cll, C12, C13 is set into operation. If the initial two elements are MM, SM or SS, the remaining five units can be passed to a teleprinter or retransmitted without change, but the fourth combination MS is indicative of the necessity of a translation operation. The two initial elements are examined by a threestage counting chain C16 such that successive pulses applied via gate G49 cause the discharge across gap N to move to gap M and then to gap S. Reception of signals not requiring translation of the five-unit signal.-In these cases tube N or M of chain C16 is fired and timing pulses at 50, 70 ... 130 ms are effective to pass received marking impulses to tube 1 of register chain R11, the pattern on the register being stepped by pulses at 40 ... 120 ms in conjunction with pulses Ps. Assuming that precisely three spacing elements occur in the received signal, the noerror tube NE is fired and pulses at 29, 49 ... 109 ms allow marks from tube 5 to operate tube M0 of the retransmitting flip-flop F13, the latter being triggered to the space condition at the instants 8.8, 28.8 ... 128.8 ms If the error tube E of the indicator F12 is fired, a pulse at 49 ms passes through the gates G51, G43 to fire tube MO to produce a mark as the second element of the five-unit code so that the five-unit code transmitted is SMSSS which produces linefeed, in either case group of the receiver, such operation being indicative of an erroneously received signal Reception of signals requiring translation of five-unit code.-In these cases the tube S of the ch