Patent GB-827034-A (GB)
Title: Telegraph signal generator for producing signals to which distortion is imparted for testing purposes
IPC: H04L25/04
Filed: 1957-08-13
Abstract: 827,034. Code telegraphy. TELETYPE CORPORATION. Aug. 13, 1957 [Nov. 27, 1956], No. 25526/57. Class 40 (3). In a telegraph signal generator for producing signals to which predetermined distortion is imparted for the purpose of testing and employing a multi-stage electronic distributer having a plurality of stages which receive potentials indicative of the different permutation code elements of a signal and which are energized in succession by sequential driving pulses to cause the code elements of the signal to be transmitted in succession over an output line by means of a circuit for establishing the requisite space-mark and mark-space transitions in the signal and in which the driving impulses for the distributer are derived from a constant frequency source through a succession of frequency-dividers each having a plurality of stages which are similarly energized in succession, the circuit for establishing the spacemark and mark-space transitions of the signal is controlled by a coincidence circuit serving to introduce the desired distortion by advancing or retarding selected ones of the said. transitions under the joint control of a conditioning potential derived from the electronic distributer as the stages thereof are successively energized and which varies in dependence on the nature (spacing or marking) of the permutation code element potentials applied to the respective distributer stages and of a momentary operating potential or combination of potentials produced respectively by energization of a selected stage in the last of the succession of frequency dividers or by the simultaneous energization of the selected stage in the last of the succession of frequency-dividers and of a selected stage in one or more of the preceding frequency-dividers. The code elements selectively set up on the contacts 15 ... 19 controlled by a perforated tape transmitter are sensed and transmitted to an outgoing line leading to a receiving relay 50 by a magnetron type distrubuter 26 in which the beam is switched to the targets 23 in succession by negative pulses applied alternatively over conductors 114, 116 to grid electrodes 27, 28. The arrangement is normally operated to provide a stop element of duration greater than that of the start element and of each code signal elements by the use of separate crystal-controlled oscillators 61, 62 of two different frequencies. When the distributer 26 is in the stop-stage during which the coil 20 of the stepping magnet of the tape transmitter is energized, a low potential at junction 32 is applied over conductor 63 to cut off the valve 64 of a flip-flop so that a positive potential is applied to the suppressor grid 68 of a pentode valve 69 which amplifies the pulses passed from the valve 76 associated with the valve 62 of the circuit of lower frequency. At the same time the valve 66 conducts and applies a negative pulse to the suppressor grid 72 of the valve 73 which is rendered non-conductive for the pulses from the valve 121 pertaining to the circuit of higher frequency. The pulses amplified by the selectively operated pentode valve pass over a conductor 74 to a bi-stable valve circuit 82, 83 producing alternate negative pulses over conductors 84, 86 to step a frequency-dividing magnetron device 87 to its tenth position in which it passes a pulse over conductor 88 to control a further flip-flop circuit 92, 93 to produce negative pulses alternately over conductors 94, 96 to step a second frequency-dividing magnetron device 97, which in its final position passes a pulse over conductors 98 to flip-flop 102, 103 providing alternate negative pulses over connections 104, 106 to step a third frequency-dividing magnetron device 107 which in its tenth position provides a pulse over conductor 108 to control a flip-flop 112, 113 producing the negative pulses over the conductors 114, 116 to effect the stepping of the beam of the magnetron distributer 26 over the targets 28 associated with the start and stop elements and the code signal elements. At the end of the stop element when the beam is switched to the target 23 of the start element stage, the potential at the' point 32 rises and the valve 64 conducts so that the pentode 69 is cut off and the pentode 73 is conditioned to amplify the pulses from the oscillator 61 of higher frequency corresponding to the shorter duration of the start and signal elements. Generation of marking-bias signal.-When the generator is to be operated to produce signals with a predetermined percentage of marking bias, i.e. the space-mark transitions are advanced relative to the space-mark transition at the beginning of the start signal element, a switch 10, Fig. 4, is moved to the contact MB and switches 11, 14 engage the "bias" contact, whilst each of the switches 12, 13, Fig. 2, is moved to the position MB-SED. The contactors 141, 142 are moved to engage contacts associated with target electrodes of the frequency-dividing tubes 47, 97 representing respectively 10% and 1% distortion in terms of the duration of a code element, and the contactors, as indicated, are set for a bias distortion of 11 % and in the case of marking bias the selected terminals are connected to the ninth stage of each of the frequency-dividers 97, 107. When the stop-stage is reached, a lowered potential at the point 32 is passed over conductor 36 to cut off valves 37, 39, Fig. 4, and make valve 38 conducting. The positive pulse over conductor 41 is not able to pass rectifier 44 or high resistor 46 to operate valve 47 controlling the receiving relay 50. If it is assumed that the final element of the preceding signal was spacing the potential at the point 45 is raised and valve 47 conducts so that relay 50 is operated. Also valve 52 conducts and makes valve 53 non-conducting to hold the valve 47 conducting until a negative pulse reaches the point 45, Fig. 4. When the stop stage of the distributer 26 is cut off the potential at the point 32 rises and valves 37, 39 conduct so that a negative pulse passes via diode 44 and cuts off valve 47 so that a start element is transmitted by relay 50. This element has its normal duration unless the potential at the point 45 is changed. Assuming that the first code element is marking so that the space-mark transition is to be advanced to provide marking bias, the contact 15 is closed and a negative potential appears on conductor 126 cutting off valves 127, 129 so that a positive pulse is applied over conductor 130 and rectifier 131 to a valve 133 which conducts and passes a negative pulse to the grid of the valve 138. During the time when the divider 107 is in its 9th stage, and the frequency-divider 97 reaches its 9th stage in respect of the time duration of the start element, negative impulses are applied simultaneously over resistors 143, 146 to the grid of the valve 138 having its other grid connection at point 136 already biased negatively so that the valve cuts off and a positive pulse passed over conductor 148 to the junction point 45 makes valve 47 conductive to transmit the mark polarity commencing 11 % before the end of the start element. Generation of spacing-bias signals.-For signals with spacing-bias, i.e. in which the spacemark transitions are delayed relatively to normal, the switch 10, Fig. 4, is moved to the position SB and the switches 12 and 13, Fig. 2, are moved to the positions SB-MED, the contactors 141, 142 being set for 11% distortion. In the start-stage of the distributer 26 a positive potential is applied over conductor 36 making valves 37, 39 conducting so that a negative potential is applied over conductor 41 and rectifier 44 to make valve 47 non-conductive to provide a spacing element and for the line 49. When the first impulse stage is reached the closed contact 15 effects lowering of the voltage on the line 36 so that valve 39 becomes non- conductive but the positive pulse cannot reach the junction point 45. The positive pulse from the valve 39 passes via conductors 41, 153 and switch 10 to make valve 133, Fig. 2, conducting so that a negative pulse is applied to the grid of the valve. When negative potentials are also applied from the target electrodes of the frequency dividers 97, 107 to the resistors 143, 146, respectively, the tube 138 is cut off and a positive potential is applied over conductors 148, 149 to the point 45 so that the valve 47 conducts and passes a marking element to the receiving coil 50. This condition persists until the next spacing element occurs which is again lengthened to produce the desired spacing bias. Generation of signals with spacing-end distortion.-For such signals the transitions of mark to space are advanced from normal relative to the initiation of the starting impulse and the switch 10, Fig. 4, is moved to the position SED, whilst the switches 11, 14 are moved to the position ED. The switches 12 and 13, Fig. 2, are moved to the position MB-SED, and the switch 154, Fig. 3, is moved to the position ED. In the stop stage of the distributer 26, a reduced potential is applied over conductor 36 so that the valve 39 is cut off and a positive potential is applied over rectifier 155 to the junction-point 45 to make valve 47 conducting to produce a marking element. As the switch 154 is closed a decreased potential is applied over conductor 126 so that the valve 128 conducts and passes a negative pulse which is blocked. When the start stage of the distributer 26 is operated a rise of potential on lead 36 makes the valves 37, 39 conductive, but the negative pulse over lead 41 is blocked. At the same time, a negative pulse is passed over conductor 54 to the junction point 45 so that valve 47 cuts off to produce the start element. At the first code element stage of the distributer 26, a reduced potential over lead 36 cuts off valves 37, 39 so that valve 47 conducts to pass a marking element to the coil 50. Also at this stage since the