Patent GB-651889-A (GB)
Title: Improvements in electronic counters
IPC: H03K23/82
Filed: 1948-06-23
Abstract: 651,889. Counting-apparatus. METROPOLITAN - VICKERS ELECTRICAL CO., Ltd. (General Electric Co.). June 23, 1948, No. 16892. [Class 106 (i)] [Also in Group XL (c)] An electronic counter comprises a valve having an impedance in its cathode circuit and a capacitor connected to apply a variable voltage to the control electrode of the valve, the grid is normally biassed to a given voltage and a rectifier connected in the control electrode circuit limits the negative voltage excursions of the electrode relative to the cathode of the valve. The Figure shows a scale of ten counter circuit in which positive - going input pulses are applied via capacitor 11 and are clipped by grid current flow and amplified in valve 1. The negative output pulses are applied via rectifier 43 to valve 18 of the trigger pair comprising valves 17, 18, this valve being arranged to be normally conducting in the stand-by position by the operation of switch 41. The trigger-pair is changed over by the first incoming pulse and is changed back by the second pulse so that one output pulse is produced for each two input pulses. The operation of switch 16 enables the time at which the count is commenced and terminated to be controlled. Rectifiers 45, 46 in the gridcathode circuits of valves 17, 18 provide a discharge path for their associated grid capacitors 34, 37 via the conducting valve so that if, for example, valve 18 is cut-off and capacitor 37 is charged negatively, a discharge path is provided by rectifier 46, resistor 47, and the conducting valve 17. The values of biassing resistors 33, 36 thus do not appreciably effect the recovery time of the circuit which will handle pulses occurring at a high repetition frequency. The pulses at the anode of valve 18 are applied via the clipping and phase inverting stage 48 to the ring counter circuit comprising valves 57-61. in which only one valve is conducting at an instant. The operation of switch 41 causes valve 57 to be normally conducting and thus all the other valves in the ring to be cut-off. Successive positive-going pulses on lead 55 cause each valve in the ring  to be rendered conducting in succession, with the other valves then being cut-off. Rectifiers 122-126 provide discharge paths via the conducting valve for the grid capacitors 92-96 as described in connection with valves 17, 18 so that pulse trains having a high repetition frequency may be handled. The metering or counting circuit comprising meter 127 and resistors 130-134 is such that no current flows through resistor 134 when valve 17 is cut-off and that one unit of current is indicated by the meter when valve 17 is conductive. Similarly, no current flows through resistors 130-133 when valves 58-61. respectively are non- conductive and the current flow through these resistors is 2, 4, 6 and 8 units when valves 58-61 respectively are in turn conductive. Thus meter 127 will indicate the number of input pulses up to a maximum of nine which have been applied, Fig. 3 (not shown). When at the tenth input pulse valve 61 reverts from the conducting to the non-conducting state the positive pulse at its anode triggers over the cathode coupled flip-flop circuit comprising the double triode valve 137 which after a period reverts to its normal state, thus producing an output pulse at terminal 154. A similar scale of hundred counter may be fed with input pulses derived at terminal 156 from the anode of valve 61. Rectifier 144 provides a discharge path for capacitor 142 of the flip-flop circuit 137.