Patent GB-799699-A (GB)
Title: Start-stop to multiplex signal converter
IPC: H04L5/24
Filed: 1956-09-07
Abstract: 799,699. Multiple telegraph systems. TELETYPE CORPORATION. Sept. 7,1956 [Oct. 25, 1955], No. 27468/56. Class 40 (3). In a converting arrangement for connecting a start-stop signal transmitter to the transmitting distributer of a multiplex telegraph system in which the signal code elements of the startstop signals are stored by means of a start-stop distributer in a first-level storage device from which they are transferred to a second-level storage device for transmission over the multiplex system under control of operating pulses received from the multiplex distributer, the first-level and second-level storage devices each comprise a series of bi-stable storage circuits for storing individual code impulses of the signals which are transferred from the first-level storage device to the second-level storage device by means of a transfer potential which is applied to gate circuits interconnecting the corresponding bi-stable storage circuits of the two storage devices under the joint control of the start-stop distributer and of the received operating impulses. In the arrangement described the transfer potential is generated and applied to the gate circuits under the control of two additional interconnected bi-stable circuits, one of which is operable to allow the transfer potential to be generated under the control of a received operating pulse only when the other additional bi-stable circuit is in operated condition and, when operated, permits the continuation of the transfer potential until restored to an unoperated, i.e. normal, condition under the control of the stop stage of the start-stop distributer, and the other additional bi-stable circuit is operable under control of the start stage of the start-stop distributer and is returnable to its unoperated condition by the restoration of the first-mentioned additional bi-stable circuit to its unoperated condition. The startstop oscillator, the start-stop distributer, the bistable circuits, and other circuits employed in the arrangement include, as operative elements, transistors which function by being switched from a conductive to a relatively non-conductive condition, and vice versa. In the rest condition with the stop element of marking (positive) potential on the line 14, the circuit comprising transistors 24, 31 is in oscillation and the oscillations fed from the winding 34 of a transformer 33 are amplified by a transistor 36 and fed via rectifiers 40, 43 to the bases of transistors 42, 26 so that normally the transistor 46 is conducting. When the start element is received the oscillations cease and the transistor 46 is cut off by the positive potential at point 44 applied to its base so that the transistor 42 becomes conductive. A positive pulse is applied to normally conducting transistor 52 forming with transistor 53 a one-shot multivibrator and with transistor 53 conducting a positive pulse of predetermined time duration is applied to a gate 60. If, when the multivibrator returns to normal and applies a negative pulse to rectifier 61 the spacing start element is still present on the line 14 so that a negative pulse is applied from transistor 46 to rectifier 59, the gate opens and the transistor 67 becomes non-conductive cutting off transistor 68 and also a transistor 71 which in its conductive state prevents a circuit comprising transistor 72, inductance 73 and capacitor 74 from oscillating. With transistor 71 cut off, the sinusoidal oscillations passed over conductor 75 are changed to rectangular form by transistors 76, 78 and 79, made conducting in sequence, and passed to a ringing circuit comprising diode 81 and inductance 82 co-operating with a transistor 84 to provide over conductor 86 negative pulses which are applied to a start-stop distributer comprising normally conducting transistor 96 and non-conducting transistors 90 ... 95. When transistor 96 becomes non-conducting, it renders the transistor 90 conducting and also applies a negative pulse over conductor 98 to the diode 64 so that the oscillating circuit is maintained until the transistor 96 again conducts and the stop element is present on the line 14. The negative pulses over conductor 86 are also applied over conductor 101 to interconnected transistors 102, 103 forming a one-shot multivibrator producing pulses of short duration which occur at the middle of the received signal elements and which are applied over conductor 104 and rectifier 106 to a gate point or junction 108. When a mark element is received the transistor 46, Fig. 4, becomes non-conducting and applies a positive pulse over conductor 109 to diode 107 so that the gate opens and transistor 111, becoming non-conducting, passes a pulse over conductor 112 to rectifiers 113 ... 117 which receive five pulses in sequence from the transistors 91 ... 95 of the distributer, the transistor 90 corresponding to the start element. The five information elements are passed to bistable circuits comprising, Fig. 6, transistor pairs 131-138, 132-139 ... 135-142, of which the transistors 131 ... 135 are normally conducting. During, or prior to, the storage of the signal in the first-level bi-stable circuits 131-138 ... the connector 150, Fig. 7, which passes the pulses from the second level storage to the multiplex distributer, provides a pulse over conductor 151 which makes non-conducting the transistor 152 of a one-shot multivibrator and by a negative pulse over conductor 154 renders transistor 153 conducting and also makes a transistor 157 more conducting. When the transistor returns to its normal state and with the start-stage transistor 90 conductive and causing transistor 159 to pass a positive pulse over conductor 161, the transistor 162 ceases to conduct and a negative pulse at its collector electrode is passed over conductors 164, 168 to point 169, Fig. 7, so that capacitor 155 discharges rapidly and restores transistor 152 to its normal conducting condition. When the transistor 157 becomes less conductive, and with transistor 163 conductive, the junction point 171, Fig. 7, becomes positive and renders transistor 173 non-conductive. Transistor 174 of the bi-stable circuit 173, 174 becomes conductive and makes transistor 178, Fig. 6, non- conductive or less conductive, so that a positive pulse is applied to the common conductor 179. The transistors 138 ... 142 will be selectively conducting according to the marking elements of the signal and apply positive potential to the corresponding diodes 188, 211 ... 214, and in combination with the positive potential from conductor 179 to the diodes 181 ... 185 will pass positive pulses to the transistors 192 ... 196 forming with transistors 200 ... 204 the second level bi-stable storage circuits. The positive potential on conductor 179 is also applied to junction point 216 and to normally conducting transistor 217 which cuts off and renders conducting the associated transistor 218 which passes a marking pulse over conductor 226 to the sixth connecting terminal of the connector 150. When the stop stage 96 of the start-stop distributer operates, a pulse is applied over conductor 230 and diode 231, Fig. 6, to junction point 232, Fig. 7, and via diode 233 is effective to cut off transistor 174 and make transistor 173 conducting so that a positive potential is applied over conductors 239, 241 to render transistor 163 non-conducting and its associated transistor 162 again conductive. If the multiplex distributer transmits pulses from all the transmitters and supplies operating pulses at a faster rate than that at which successive signals are received from the individual start-stop signal transmitters, two incoming operating pulses received within the period between successive operations of the start transistor 90 would result in a transmission of the same signal twice. If an operating pulse is received a second time before the transistor has a chance to operate a second time, there will be no signal transfer to the multiplex transmitting distributer on one of the occasions on which this might occur, and instead a " service " blank signal with all the elements, including the sixth element supplied over conductor 226, spacing. In the case in which the code elements have been transmitted by the multiplex distributer and a control potential has been applied over conductor 151, but the start transistor 90 has not operated, the transistor 162 will still be conductive and a relatively high potential transmitted to junction point 169 so that the one-shot multivibrator 152, 153 will execute a slow-timed operation. Also the positive potential on conductor 151 will be applied to transistor 243, Fig. 7, which will become non- conducting and pass a positive pulse to common conductor 244 to render non-conducting any transistors 200 ... 204 rendered conducting by marking elements of the previous signal. Also transistor 218 is made non-conducting so that the sixth impulse to be passed by the multiplex distributer will also be a spacing element. When the multivibrator 152-153 restores, transistor 157 becomes less conductive a positive potential is applied through diode 167, bi-stable circuit 173, 174 is not operated and transistor 178, Fig. 6, remains in its normal condition with the result that any signal set up on transistors 138 ... 142 is not transferred. When the next signal is received and start transistor 90 operates, the transistor 159 is driven towards non-conduction and the bistable circuit 162, 163 operates. Also a potential rise is passed over leads 250, 251 and restores to the non-conducting condition any transistors 138 ... 142 which had been left conducting in response to corresponding marking elements in the preceding signal. When the next signal, assumed to be " all-marking," is received, all the first level storage circuits will be operated, but these will not be transferred because of the low potential on the diodes 181 ... 18