Patent GB-733071-A (GB)
Title: Improvements in or relating to apparatus for producing electric telegraph signals
IPC: H04L17/02
Filed: 1952-03-06
Abstract: 733,071. Printing telegraphy transmitters. GENERAL ELECTRIC CO., Ltd., BAYLISS, A. J., and PEDDLE, E. A. R. March 6, 1953 [March 6, 1952], No. 5867/52. Class 40 (3). A teleprinter transmitter utilizes cold cathode valves for coding, storing and transmitting telegraph signals. Switches 1, 2 ... 8 are typical of thirty-one switches operated by teleprinter keys. Depression of any key connects positive supply to the anode of a respective cold cathode coding valve 9 having five cathodes representative of the five elements in the code. Cathodes representing mark elements in the particular character code are connected to respective bus-bars 13 to 17 while cathodes representing space elements are left unconnected. Thus when a key is operated certain selected bus-bars are raised to a positive potential. Five code-element stores are provided, each comprising a bi-stable arrangement of two cold cathode valvesone in each group of valves 26 to 30 and one in the group 31 to 35. It is arranged (as described below) that prior to a key .being operated each valve 31 to 35 is conducting and, therefore, each valve 26 to 30 is non-conducting. The bus-bars 13 to 17 are connected respectively to the grids (trigger electrodes) of valves 26 to 30 so that when a key is depressed the valves 26 to 30 which correspond to mark elements are fired and the code of the character selected is thus stored by the appropriate ones of valves 26 to 30 being conducting for mark elements and appropriate valves 31 to 35 being conducting for space elements. The anodes of the " mark " valves 26 to 30 are fed via a relay LK so that as soon as a code is stored the relay is operated. Contacts LK1 remove the positive supply from the key switches 1 to 8 &c. and apply it to the grid of a cold cathode valve 41 which is the first in a counter chain 41-47. (The Provisional Specification utilizes a condenser connected to the left-hand contact LK1, as shown, but the Complete Specification requires this to be replaced by a resistor). The valves 41 to 47 are arranged to fire in sequence upon successive cycles of an oscillator valve 49 enclosed in a box 50 with a lamp 51 to maintain a constant oscillation frequency of about 50 c/s. As each of the valves 41 to 47 fires it extinguishes the previous one. Signals are sent to the line 61, 62 by contacts L1 (shown in the operated position) of a relay L in the cathode circuit of one valve 63 of a bi-stable pair 63, 64. When valve 63 is fired relay L is operated and a mark signal is sent; when valve 64 is fired 63 is extinguished, relay L releases and a space signal is sent. The grids of valves 63, 64 are connected respectively to valves 67, 68, each of which has six anodes with a common cathode, such that if any one anode has applied to it a positive voltage sufficient to fire the valve the associated valve 63 or 64 is triggered. The first five anodes of valve 67 are connected respectively to the cathodes of " mark " storage valves 26 to 30 while the first five anodes of valve 68 are connected to the cathodes of "space" storage valves 31 to 35. Thus, whenever a storage valve is conducting a positive bias is fed to the associated anode in valve 67 or 68. These anodes are also connected in pairs via condensers to. receive sequential pulses from the cathodes of the counter valves 42 to 46. The sixth anodes of valves 67 and 68 have a permanent positive bias and are coupled respectively to the cathodes of the last valve 47 and the first valve 41 of the counter chain. The valve 47 and therefore valve 63 are normally conducting and thus relay L is operated and " mark " condition is applied to the line. To ensure that valve 47 is conducting upon first switching on a key switch 91 is provided whereby a positive bias may be supplied to its grid. When a character code has been stored relay LK operates and its contact LK1 biases valve 41 such that the next positive pulse from the oscillator 49 causes valve 41 to fire. This applies a positive pulse to anode 82 of valve 68, fires valve 64 which extinguishes valve 63, thereby releasing relay L and a " start " (space) signal is sent to line. The next positive pulse from oscillator 49 fires valve 42 which pulses the first anodes of both valves 67 and 68. One of these anodes will be biased positively according to whether a mark or space code element is stored on valve 26 or 31, and hence the appropriate valve 67 or 68 and, therefore, 63 or 64 will be fired and relay L will operate or not to signal the stored condition to line. This procedure continues for the other four code elements and then the last valve 47 of the counter chain is fired. This pulses the anode 76 of valve 67 and causes a " stop " (mark) condition to be applied to line. The final counter valve 47 also triggers valve 87 which is connected in a mono-stable circuit with valve 86 which latter is permanently biased to be normally conducting. Thus, when valve 87 fires, valve 86 is extinguished but re-fires and sends a positive pulse from its cathode to the grids of storage valves 31 to 35. This ensures that these valves fire and hence that valves 26 to 30 are extinguished in readiness to store the next character code keyed. The extinction of valves 26 to 30 causes relay LK to release and a further character code may be stored immediately contacts LK1 restore. The slight delay introduced by valves 86 and 87 ensures that the "stop" signal is of longer duration than an ordinary " mark " element. Coding valves 9 may have six cathodes although only five or less are used, or each valve 9 may be replaced by the appropriate member of separate diodes or rectifiers. Automatic transmission of identity.-The arrangement shown in Fig. 2 provides means for sending twenty characters, such as a stationidentifying signal, automatically. Twenty-one valves, of which nine only (101 to 109) are shown, are connected in cascade such that when one fires the preceding one is extinguished and the succeeding one is prepared by a positive bias on its grid. The first valve 101 has its grid permanently positively biased and coupled to a " Here Is " key 111 while the grids of the remaining twenty valves are coupled to the relay contacts LK1. The cathodes of the twenty valves, 101 . . . 108 &c., are connected to terminals T1 to T20 in a patching field 113 whereby they may be cross-connected to any of the key switch terminals T<SP>1</SP>1 to T<SP>1</SP>31 (see also Fig. 1). When key 111 is operated a positive pulse fires valve 101 and thus a positive supply is connected to the associated key switch terminal (T<SP>1</SP>29 as shown). This causes the appropriate character code to be transmitted as described above for mechanical operation of a key switch (6 in Fig. 1). Relay LK is thus operated and when it releases after transmission of the code the contacts LK1 apply a positive pulse which fires the already positively biased valve 102. The next selected key switch terminal (T<SP>1</SP>1, as shown) thus receives a positive supply and the second character code is transmitted. The positive pulse occurring when relay LK releases after this transmission fires valve 103 and causes the third character to be transmitted. This procedure continues automatically till all twenty codes have been transmitted. Rectifiers 115 prevent feed-back from one cathode to another should the same code be required more than once in the identifying signal. Complete teleprinter.-This transmitter may be combined with the receiving apparatus described in Specification 733,070 to form a complete teleprinter. In this case the receiver valve 122 (Fig. 2) which is associated with the character D has its cathode connected to the key 111 via a switch 124 which is closed and opened by the figure-shift and letter-shift electromagnets respectively. Thus when the " Who Are You " code is received (i.e. character D code preceded by the figure-shift code) the valve 122 sends a positive pulse to the grid of valve 101 and automatically initiates the above " Here is " transmission.