Patent GB-670758-A (GB)
Title: Multiplex telegraph apparatus
IPC: H04L5/24
Filed: 1949-09-30
Abstract: 670,758. Multiplex telegraphy; thermionic distributers. TELETYPE CORPORATION. Sept. 30, 1949 [Oct. 15, 1948], No. 25186/49. Class 40 (iii). Thermionic distributers operating respectively at impulse speed and channel speed are used for multiplex transmission and reception of five-unit code messages. Transmitting arrangements. The impulse distributer comprises five gas-filled tubes 24 ... 28 connected in a ring circuit, each tube when fired priming the next over a delay network 31 and extinguishing the previous one over a condenser 33 connected between the anodes. Firing pulses at the impulse frequency are supplied to the control grids from an oscillator 11 over a frequency-divider 12 and squarer 14. The channel distributer comprises a similar ring of four gasfilled tubes 41 ... 44 supplied with firing pulses at channel frequency from oscillator 11 over a second frequency-divider 13, a phase-shifting network 17 and a squarer 18. The tubes 24 ... 28 and 41 ... 44 when fired supply priming potentials respectively to the control and screen grids of vertical and horizontal lines of tetrodes 58 ... 80. The anodes of these valves are connected to the respective signal contacts of four tape transmitters 51 ...54 (or of a start-stop-to-multiplex converter as described, for example, in Specification 670,761). If the first code element of the first message is a mark, tetrode 58 operates, having at the same time potential on its anode and priming potential on both of its grids, and the fall of potential on lead 91 transmits a mark over the signalling channel. The remaining elements of the first character of the first message are similarly set in succession, followed by the five elements of the first character of the second message and so on. When tube 42 fires at the end of the first character transmission, positive potential at its cathode is connected over lead 93 to fire a gas tube 96 connected in series with a magnet 98 which initiates the storing of a second code combination on tape transmitter 51. Relay 102 in parallel with magnet 98 operates slowly due to a shunt condenser 103 and opens the circuit of magnet 98 and extinguishes tube 96. Similar arrangements are provided for the other tape transmitters 52 ... 54. Receiving arrangements, Figs. 3, 4 (not shown). These are generally similar to those in Figs. 1, 2, and comprise similar distributers priming in succession a set of twenty tubes arranged like tetrodes 58 ... 80. These tubes are, however, of gas-filled type and the appropriate doubly-primed one is fired, when a mark is received, by an additional positive potential which is connected by the receiving relay to the control grids of all the tubes in parallel. The anode circuits of the tubes are connected to positive battery over magnet windings, a selection of which corresponding to the marks received is thus operated for each channel in succession. When the next tube in the channel distributer is fired, a tube corresponding to tube 96, Fig. 2, is fired to operate a printing magnet 98. A relay corresponding to relay 102 in addition to extinguishing the tube 96 removes positive battery from the anode circuits of the five tubes used in the previous selection to restore them to normal. The oscillator controlling the distributers is automatically synchronized by the received signals in the manner described in Specification 670,760, [Group XXXV]. Specification 670,762 also is referred to.