Patent GB-797754-A (GB)
Title: Improvements relating to code telegraphy
Inventor: SAUNDERS RONALD LIONEL SPENCER
IPC: H03M5/00
Filed: 1955-01-06
Abstract: 797,754. Type-printing telegraphy. GABLE & WIRELESS, Ltd. Jan. 6, 1956 [Jan. 6, 1955], No. 437/55. Class 40 (3). In a telegraph system in which 5-unit signals of 2-condition elements are converted into signals of 3-condition elements for transmission over a line, the 5-unit signal elements are set up by a change-over set of contacts and successive groups of three elements are applied by timed contacts to charge in sequence three condensers which are discharged simultaneously through the respective windings of three electromagnetic relays on the contacts of which the signals are set up as successive groups, each of three signal elements, which are converted into two corresponding 3-condition elements. The eight groups of elements such as MMM, MSS, SSM ... are converted to 00, + -, - + ... respectively, 0, + and - representing space, dot and dash respectively, and a spare combination, 0+ (space, dot) is employed as a supervisory signal. Converter arrangement at the transmitter. A tape 1 in which the 5-unit signals are perforated is fed continuously over feelers 3 which are allowed to move upwards by springs 7 under control of cams 10 on a shaft 9 so that the detection of perforations allows the feelers to rock a pivoted frame 4 so that a contact member 6 which is moved to the mark position M and is connected over contacts 11, 13 to a conductor 19 effects selective charging of the condensers C1, C2, C3 according to three elements of a group by contacts 20 sequentially closed by cams 21 on a shaft 9A rotated at a rate 5/3 times that of the shaft 9. The condensers Cl, C2, C3 are simultaneously discharged over contacts 22A, 22B, 22C through the windings of three pairs of polarized relays R1A, R1B, R2A, R2B, R3B, R3A, R3B which move their armatures 24, 25, 26 and 31, 32, 33 upwardly in response to spacing impulses. The operation of relays R1A, R2A when the first two elements are spacing prepares a circuit through the windings of two secondary relays C, D and the circuit is completed through the winding of relay A or relay B in response to the spacing or marking nature of the third element of the group of three elements of the 2-condition code. If, for example, the 3 elements are all M, the relays R1A, R1B ... R3B are not operated and none of the relays A, B, C, D is energized. The armatures 27 ... 30 of the relays A, B, C, D are normally held against their upper contacts by biasing windings. Switches LS, ES are changed over for the transmission of the two elements of the 3-condition code. In the switch position shown for LS, ES, since relays R1B, R2B, R3B are all released, positive potential is connected over contact 31 to the line L and also to earth E so that a zero (space) impulses passes to the line L. When the switches LS, ES are changed over to send the second element of the 3-condition code, positive potential is applied to the line L from the contact member 33 in its released (lower) position and is also connected to earth E over contact of switch US in its upper position and contact member 30 of relay D (unoperated) so that a zero (space) impulse is again passed to the line L. In the case of the combination SSS, all the relays R1A, R1B ... R3B are operated and secondary relays A, C, D are energized. For the first element of the 3-condition signal, positive is applied to the line L through operated armatures 31, 27 and negative is connected to earth E over armature 32 (operated) and armature 28 (unoperated) so that a dot (+) is sent to the line. For the second element of the 3-condition signal, positive is connected over armatures 33 and 29 (both operated) and negative is connected to earth over switch US and armature 30 operated so that a dot is sent as the second element of the signal, dot dot (+ +), corresponding to SSS. For the " no-tape " condition the contact member 13 engages the lower contact 12 and an idler cam wheel 14 produces a long period of the marking condition M transmitted over the line as zero current, interrupted by one or more signals of marks and spaces transmitted as corresponding 3-unit signals. To send the warning signal, the switch US is moved to its lower position and with no tape in the transmitter, or the factors 3 all operating to produce the marking condition, the first element of the 3-condition code is 0 (space). For the second element, with the switches LS, ES changed over from the position shown, positive is connected to the line L but negative is connected to earth E over the lower contact of US so that zero-dot (0+) is sent to the line L. Reconverter arrangement at the receiver, Fig. 4. Polarized relays DAR, DOR are respectively operated by the dash-and-dot elements, both relays remaining unoperated for the spacing element. Contact pairs 36, 37 and 38, 39 are connected respectively to the armatures 34, 35 of relays DOR and DAR, the contacts 36, 38 being closed by cams 40, 41 at the mid-point of the first elements and the contacts 37, 39 being closed by the cams 42, 43 at the centre of each second element of the 3-condition code representing the three units of the 2-condition code. Condensers C4, C5 are charged in series depending on whether the first element is a dot or a dash and two further condensers C6, C7 are charged in dependence on the nature of the second element. The condensers C4 ... C7 are discharged simultaneously by contacts 44 operated by cams 45 so that if an element is a dash relay DA1 or DA2 moves its armature 46, 48 to the lower position, whilst if the element is a dot, relay DO1 or DO2 moves its armature 47 or 49 to the lower position. For a space element, relays DA1, DO1 or DA2, DO2 retain their armatures 46 ... 49 in the upper positions. Armatures 51, 52, 53 of a relay SR are moved to the right when the relay is energized by the downward movement of armature 49 in response to a dot as the second element. The reconverted groups of three elements are transferred from segments 61, 62, 63 of a distributer D1 to five segments 64 of a distributer D2 by brushes B1, B2 rotated at speeds in the ratio of 5 : 3. The elements on the segments 64 are stored on condensers CR from which the signals are transmitted to an outgoing line relay OR by a distributer D3 with a brush B3 engaging additional segments 65, 66 to produce the start and stop elements of the 5-unit code combination. If, for example, the received combination is 00, the relay SR is not operated and the armatures 46 ... 49 remain in their upper position so that the reconverted elements are MMM. In response to dot dash (+ -) the armatures 47, 48 are moved to their lower positions so that the reconverted elements are MSS. If the received combination is, for example, dash dot (- +), armatures 46, 49 move into their lower positions, and relay SR is energized so that the armatures 51 ... 53 are moved to their right-hand positions. In this case the 3-unit group is SSM. When the supervisory signal 0+ (space dot) is received, the armatures 46, 47 of relays DA1, DO1 remain in their upper positions and relay D02 is energized so that relay SR is operated. A relay ER is operated over armature 46 and an additional armature 68 moved to its contact 69 by the operation of relay SR completes the circuit of an alarm relay AR which at contact 71 operates an alarm bell AB. The combinations dot dot (+ +) and dash dot (- +) cannot operate the alarm as relay ER cannot operate if the first element is a dash, and if the first element is a dot, the movement of armature 47 to its lower position removes the operating potential for the relay AR.