GB766826A - Improvements in or relating to checking circuits - Google Patents

Abstract

766,826. Digital electric calculating-apparatus. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. May 5, 1955 [May 25, 1954], No. 15321/54. Class 106 (1). [Also in Group XL (b)] In a circuit arrangement for checking the validity of a coded signal represented by an electrical condition applied to a predetermined number out of a fixed number of leads, each lead controls, according to whether or not it is subjected to the electrical condition, the priming potentials applied to a series of gas discharge tubes, and the plurality of series of tubes are interconnected so that a pulse applied to the first series is repeated by a tube in each successive series and provides an output signal only if the correct predetermined number of leads are subjected to the electrical condition. General.-In the circuit described a valid signal consists in a rise in potential on any two of five input leads 10 ... 14. A positive testing pulse enters at terminal 15 and, if the signal is a valid one, a positive output signal appears on terminal 18. In the particular circuit described an output signal is obtained also when positive signals are applied to all five input leads simultaneously ; this is desirable in using the circuit for automatic telephone exchange monitoring. The testing circuit may be associated with a plurality of storage devices or circuits in succession. Detailed operation.-If a positive signal appears on lead 10 the trigger electrode of tube VK1 will be raised from cathode potential to about +50 volts and the cathode of tube VK2 raised to a similar value. Thus, when a positive test pulse appears at terminal 15 tube VK1 will strike if lead 10 has been marked; otherwise tube VK2 will strike. The rise in cathode potential of the conducting tube is communicated to a further pair of cold cathode gas discharge tubes, either VK3/VK4 or VK6/VK7, controlled by the condition of the second input lead 11; the left-hand one of the selected pair strikes if lead 11 is marked and the right-hand one strikes if lead 11 is not marked. Separate output leads are taken from the cathodes of tubes VK3 and VK7, but a common output channel is provided for tubes VK4 and VK6 via a combining tube VK5 which has its cathode connected to that of the tube VK6 and is connected so as to be fired whenever the tube VK4 is fired. The three output leads from this series of tubes are capacitatively coupled to further pairs of tubes in the series controlled by the lead 12, combining tubes VK10, VK13, again being employed to reduce the number of circuits and components in subsequent series which are arranged to provide an output signal on lead 18 if the input leads carry a valid signal as described above. The checking circuit may be used in conjunction with a fault recorder timing circuit, the signal appearing at lead 18 serving to reset the timing circuit which, in the absence of such a signal, would cause the fault recorder to be operated after a pre-arranged interval.