Patent GB-670874-A (GB)
Title: Improvements in or relating to telegraph repeaters
IPC: H04L25/24
Filed: 1948-02-27
Abstract: 670,874. Code telegraphy. WESTERN ELECTRIC CO., Inc. Feb. 27, 1948 [Oct. 6, 1942], No. 6071/48. Class 40 (iii). In a telegraph signal repeater, a signaloperated relay, in response to the first impulse of a series of impulses controls a normally inactive impulse generator, preferably an electronic oscillator, to set the generator into operation to produce a series of pulses in approximate synchronism with the impulses of said series, a pulse produced by the impulse generator causing the energization of the transmitting relay in accordance with the condition of the recovering relay and the impulse generator being rendered inactive a predetermined interval after being set into operation. The predetermined interval may be determined by a circuit which counts a fixed number of impulses produced by the generators. The impulses received over a line 13 are applied to a polarized relay 11 having a biasing winding fed from a battery 12 and having its armature moved to " spacing " contact S in response to current interruptions, The windings of the transmitting relay 19 are connected to the cathodes of two cold-cathode discharge devices 17, 18 whose anodes are connected through resistances 76, 77, conductors 74, 72, resistances 73, 24 to the positive pole of a battery 26. An opposing voltage, namely that from the negative pole of a battery 31, is connected via resistances 29, 25 and to the anode of device 17 or 18 according to the operation of the armature of the relay 11 to its marking or spacing position. When marking current is flowing over the line 13, negative voltage from battery 31 is applied over conductor 32 to the cathode of a coldcathode device 34 which is maintained in a conducting condition and prevents an oscillating circuit comprising inductances 39, 43, and a double triode valve 46 from operating. The frequency of the circuit is determined by the inductances 39, 43 in combination with adjustable capacitance comprising arrangements of condensers 55, 56, 57 connected selectively to contacts of two pairs 51, 52 and 53, 54 of switch members-the arms of a pair being moved simultaneously. The pair 53, 54 provides a coarse adjustment and the pair 51, 52 is utilized to obtain a fine adjustment of the capacitance value to be employed in the oscillating circuit. When, in response to the start impulse, the armature of the relay 11 moves to the space contact S, the discharge device 34 is rendered non-conducting and the oscillation generator is set into operation. The oscillations produced by the left-hand section of the double triode 46 apply positive pulses to the grid of the right-hand triode section and each time this triode passes from the conductive to the non-conductive condition a positive impulse is applied to the secondary winding of a transformer 66. The potentiometers 59, 63 in the cathode and plate supply circuits allow of the phase displacement of the pulses generated in the secondary of the transformer 66 in relation to the pulses generated by the oscillator. The positive impulse is applied simultaneously to the anodes of the devices 17, 18 and will render conducting that device which, by the position of the armature of the relay 11, is not subjected to the negative voltage from battery 31. The firing of the device 17, 18 results in a pulse applied via condenser 27 to the other device so that it is deenergized. The oscillating impulses of the circuit including the valve 46 are applied via resistance 82 to the grid of the triode section of a multiple valve 81, the left-hand section having its grid and anode tied so that it is effectively a diode. The voltages derived from the secondary of a transformer 83 when the triode section becomes conductive render the diode section conductive and pulse is applied from the cathode of the diode to the grid of the right-hand triode of a double triode valve 89 and simultaneously to a condenser 91. The grid bias of the right-hand triode is such that it does not conduct until seven impulses corresponding to a start impulse, five code impulses and a stop impulse have been applied to the condenser 91. When the right-hand triode conducts, the left-hand triode-which is normally conducting-is made non-conducting by discharge of a condenser 96 connected to the anide of the right-hand triode and, as a result, generates an impulse which is positive at the anode and negative at the cathode of the device 34, and if the relay 11 has returned to the normal stop condition, negative voltage is also applied to the cathode so that the device 34 becomes conductive and disables the oscillator. If the relay has not returned to the stop (marking) condition, the oscillator generates further impulses and will be disabled at the end of the additional seven pulses. When anode current in the left-hand triode ceases-the condenser 96 charges through a resistance 97 and again makes the left-hand triode conductive so that the potential of its anode is reduced and condenser 91 is discharged with the result that the right-hand triode is again rendered non- conductive. In a modification, Fig. 2 (not shown), the control of the oscillator which produces the auxiliary voltage for the firing of the coldcathode discharge device 17 or 18, is effected by a counting chain comprising seven coldcathode discharge devices of which the seventh device, associated with the stop condition, is normally conducting, and in this condition prepares the first device to be operated in response to the first of the pulses generated by the oscillator. The impulses from the oscillating circuit are applied to the devices 17, 18 via condensers in place of the transformer 66 utilized in Fig. 1.