Patent GB-637451-A (GB)
Title: Improvements relating to code telegraphy
IPC: H03M5/00
Filed: 1947-05-07
Abstract: 637,451. Code telegraphy. CABLE & WIRELESS, Ltd., and HIGGITT, H. V. May 7, 1947, No. 12382. [Class 40 (iii)] In a telegraph system using an. equal-length code, the transmitter sends the marking and spacing units of a primary equal-length code and comprises means to transmit additional signal units to form longer equal-length signals all of which have the same total marking value on the basis that each additional unit has ascribed to it a particular marking value which is the same in all the signals, but the additional signal units do not have the same marking values in a given signal, and in which the means for transmitting the additional signal units are operated in dependence on the number of marking units in the primary equal-length code part of each signal. The sixth, seventh and eighth signal units added to a primary five-unit code signal have, for example, marking values of one, two and two respectively, but the seventh and eighth units are not normally transmitted as signal units of greater amplitude. Transmitter arrangement. In an arrangement, Fig. 1, for transmitting additional units according to a first tabulated scheme, indicated in the Specification, supplementary relays F, G, HA, HB are provided in conjunction with relays A, B, C, D, E, operated by peckers Pa ... Pe controlled by a perforated tape, the latter relays being locked, on operation, over contacts 5 engaged by armatures a1 ... e1 associated with a brush 7 moving over a continuous ring 8, and the marks of the primary five-unit signal are transmitted over operated armatures a2 ... e2 and segments S1 ... S5. A series of contacts 13, 14, 15 ... 20 selectively engaged by a single armature a6 and double armatures b6 ... e6 is connected so that with none, two or four of the relays A ... E operated by zero, two or four marking units of the primary five-unit signal, the relay F is operated to apply a marking unit over contact 21 to the segment S6 for the first of the additional units. A relay HA is connected so as to be operated by armatures a4 ... e4 over the released contacts when the first five units contain no marking units and a relay HB is operated over contacts engaged by armatures a3 ... e3 when the signal contains five marking units. Since relay HA is released if the first five units include one or more marks and the relay HB is energized solely by the occurrence of five marks in the primary five-unit signal and relay F is in its released position on the occurrence of one, three or five marking units in the primary signal, a marking unit will be applied to the segment S8 over operated armature ha and released armature hb when the primary signal contains no marks. In the cases of one and three marks in the primary signal, relay F will be in its released position and a marking unit will be applied from battery 10f over contact 29 and released contact hb to the segment S8. In the case of two and four marks relay F is energized and relay HA released, and in the case of five marks relays F, HA are in released position, but relay HB is energized and prevents the transmission of a marking unit to the segment S8. In the coding arrangement employed, a mark is sent from the segment S7 as the second additional signal unit if the primary signal contains less than three marking units and with 0, 1 and 2 marks the current through the lower winding 32 of the relay G is greater than that through the upper winding 30 so that the armature g engages the contact 35 and passes a marking unit to the segment S7. With three or more marks, the current in the upper winding 30 predominates and the operation of the armature disconnects the battery source 10g from the segment S7. In a modified transmitter arrangement for double-current working, Fig. 2 (not shown), the segments (S1 ... S8, Fig. 1) of the transmitting distributer are connected to the armatures (a2 ... c2, f, g, hb, Fig. 1) of the relays and the relay F is provided with a second armature associated with contacts engaged by the armature of the relay HA. A further modification, Fig. 3 (not shown), also adapted for double-current working, and arranged to produce additional signal units in accordance with the second tabulated scheme, has a symmetrical system of armatures and contacts operated by the relays (corresponding to A, B, C, D, E, Fig. 1) with three supplementary relays, associated respectively with the sixth, seventh and eighth segments of the distributer, replacing the four relays F, G, HA and HB of Fig. 1 and the relay corresponding to relay G, Fig. 1, is operated by a single winding. In a further modification (not illustrated), in which the first five relays are operated sequentially, a bank of counting relays, similar to the arrangement disclosed in Specification 480,150, is operated by the marking units and the final contact operated in accordance with the number of marking units of the five-unit signal is connected to add the appropriate signal units. Receiving-arrangements. The armature of the line receiving relay LR is operated to its spacing contact s by the start impulse and energizes a clutch release magnet CR which moves four brushes B1 ... B4, the brush B1 engaging segments RS1 ... RS8 at approximately the centre of the received signal impulses and selectively operating relays N, O, P ... U which lock up over contacts 65, armatures n1 ... u1, the brush B2 and a ring 66. A second set of armatures n2, o2, p2 ... s2 are connected to equal resistances 70 and the armatures t2, u2 are associated with resistances 71, each of which has a value half that of the individual resistances 70. If the received signal is balanced, relay TR is not operated when the brush B3 engages a segment 72 and when the brush B4 engages a segment 74 a clutch-release magnet CR1 is energized to rotate brushes B5, B6 by which earth is applied over contact 76, armature 75 and operated armatures n3 ... r3 to energize the windings 77 of corresponding relays SR1, SR2 ... SR5, which lock up over their armatures 81, second windings 79, a brush B5 and ring 82. Corresponding impulses are transmitted to a receiving apparatus by the brush B6, segments 90 and armatures 91 operated by the relays SR1 ... SR5. If the received signal is not balanced in respect of the predetermined marking value, the relay TR is operated and at contact 76 opens the operating circuit of the windings 77 of the relays SR1 ... SR5. At contact 84 an operating circuit is completed for one or more windings 86 of the relays SR1 ... SR5 selectively connected to battery to provide a predetermined signal combination which is passed to the receiver to print an error signal and may be passed to the transmitter station to effect repetition of the signal which has been distorted in transmission. In a modified receiving arrangement, Fig. 5 (not shown), the three additional signal units received are individually compared with the additional units produced locally at the receiver by apparatus similar to that described in the transmitter arrangement, Fig. 1, and derived by examination of the first five signal units actually received. The existence of any discrepancy resulting from the comparison effects the operation of a relay similar to the relay TR, Fig. 4.