Patent GB-670761-A (GB)
Title: Electrical start-stop to multiplex telegraph signal converter
IPC: H04L5/24
Filed: 1949-09-30
Abstract: 670,761. Multiplex telegraphy; thermionic distributers. TELETYPE CORPORATION. Sept. 30, 1949 [Oct. 15, 1948], No. 25189/49. Class 40 (iii). Apparatus for associating a start-stop transmitter with a multiplex channel comprises a start-stop thermionic distributer controlled by a start-stop oscillator, both of which are started by the start signal from the transmitter and stopped during the stop signal, the distributer controlling the storing of the code-signal elements for successive transmission over the multiplex channels. In the system shown, the incoming line 12 from a start-stop transmitter 11 is connected to the winding 13 of a magnetically-controlled diode 14 which conducts during spacing signals. When a start spacing signal is received, negative potential on lead 19 is extended through the diode to lead 17 connected to a double-diode signal-shaper tube 18 which produces a positive potential on lead 21 to prime distributer start tube 22. At the same time a negative pulse is transmitted over lead 23 to a multivibrator 24 which, after a delay determined by the circuit constants, transmits a positive pulse over lead 26 to the right-hand section of valve 27, the cathode output of which fires tube 22. The delay produced by tube 24 prevents tube 22 being fired as a result of a momentary abnormal spacing condition on line 12. The common anode connection to start tube 22 and to distributer tubes 32 ... 36 is also connected to the grid of the normallyconducting right-hand section of valve 41 which thereby becomes non-conducting as soon as tube 22 conducts and removes positive potential from lead 42 causing the start-stop oscillator 43 to start. The sine-wave output on lead 44 is squared in amplifier 46 and applied through a condenser to the grid of the left-hand section of valve 48, producing positive pulses in the cathode output lead 49 connected to the control grids of the distributer tubes 32 ... 36. Each of the tubes 22, 32 ... 36 primes the next over circuits 60 so that tubes 32 ... 36 will be fired in succession at intervals corresponding to the transmission of the signal-code elements from transmitter 11. Start tube 22 also, over lead 61, causes the momentary non-conduction of the right-hand section of valve 62 supplying anode potential to selector tubes 66 ... 70 so that any of these already fired will be extinguished. The selector tubes 66 ... 70 are successively primed by the distributer tubes 32 ... 36 and the mark signals in the signal code cause positive potential on lead 72 to fire the corresponding selector tubes. The last distributer tube 36 conditions the grid of the left-hand section of valve 41 and on the transmission of the next pulse on lead 49 this section momentarily operates, releasing tube 36. The right-hand section of valve 41 operates again and stops oscillator 43. When the multiplex apparatus, connected to plug 77, is ready to transmit, an operating pulse is sent back over the plug to lead 78, e.g. in the manner described in Specification 670,758, operating the righthand section of valve 48 which in turn blocks both sections of valve 83 supplying anode potential to storage tubes 86 ... 91 and thereby releases any of these which are already conducting. The operating pulse on lead 78 is also passed to a delay multivibrator 56 which on return to its normal condition transmits a pulse over lead 96 to the control grid of tube 97. The screen grid of tube 97 is primed when tube 53 is not conducting so that tube 97 is fired and extends a firing potential over lead 104 to such of the storage tubes 86 ... 90 as have their screen grids primed by the corresponding fired selector tubes 66 ... 70. The cathode outputs of tubes 86 ... 90 are connected over plug 77 to the multiplex distributer. If the control signal on lead 78 delayed by valve 56 reaches tube 97 at any time before the stop signal, tube 97 will transfer to tubes 86 ... 90 any signals already on tubes 66 ... 70 and the remaining signals as and when they are received. During the stop signal, when none of the distributer tubes is conducting, tube 53, which has its screen grid connected over lead 31 to the common anode lead to these tubes, is fired and due to the condenser 99 connected between the anodes of tubes 53, 97 extinguishes the latter. If no previous operating pulse has been received during the reception of the particular signal, tube 97 will have sufficient time to operate before 53 extinguishes it and the signal will be sent out. If, however, there has been a previous operating pulse during the reception of the signal and a second operating pulse occurs during the stop signal, i.e. before a new combination has been received, tube 97 does not operate and an all-blank signal is inserted. A sixth storage tube 91 is always fired by the firing of tube 97, transmitting a control signal which may be used to identify an all-blank signal which must be recorded. When an operating pulse is received during the stop signal, the potentials on the grid of the lefthand section of delay multivibrator 56 are increased, causing tube 97 to operate more quickly to prevent any loss of signal.