Patent GB-786086-A (GB)
Title: Improvements in or relating to multi-cathode tube counter circuits
Inventor: TOWNSEND RALPH
IPC: H03K29/00
Filed: 1955-03-09
Abstract: 786,086. Digital electrical calculating- apparatus. BRITISH TABULATING MACHINE CO., Ltd. Feb. 16, 1956 [March 9, 1955], No. 6920/55. Class 106 (1). In an accumulator comprising a number of stages, each of which is constituted by a multicathode discharge counting tube, cyclically operable means being provided for entering values in each stage by stepping the discharge successively on to the individual cathodes, a carry arrangement is used which comprises a load circuit for one of the cathodes (e.g. the " zero " cathode), a thyratron adapted to be fired by flow of discharge current through the load and a cam-operated switch adapted at a predetermined point in the entry cycle to apply a voltage from the thyratron to operate the next stage. Values to be entered are read from punched cards, the cards being fed past first sensing brushes to determine whether the entry is additive or subtractive and past second sensing brushes to read the value to be entered into the accumulator. The values are entered as a series of pulses. When the entry is to be additive the " real " number of pulses is relayed to the guide electrodes of the multicathode discharge tube and when the entry is subtractive a number of pulses is sent which is the " complement " of the number read from the card. For this purpose switch contacts are provided which connect the pulse generator to the guide electrodes for different parts of the card cycle for additive or subtractive entries. If an additive entry of " 5 " is to be entered, pulses corresponding to card index positions 1, 2, 3, 4, 5 are sent to the guide electrodes, a switch opening when the perforation in position " 5 " is sensed. In a subtractive entry, no pulses are sent to the guides until the perforation in position 5 is sensed. A switch then closes to allow pulses corresponding to positions 6, 7, 8 and 7 to be sent, i.e. 4 pulses, 4 being the complement to 9 of 5. The stepping pulses are fed to the input of the counting tube on line PL connected through condenser 13 and diode 14 to the guide electrodes. Each cathode is connected through a diode 18 and resistor 19 to earth line 20 and through a diode 21 to a carry line 22. Line 22 is connected through condenser 24 to the grid of a triode 26. The junction of the diode 18 and resistor 19 associated with the zero cathode is connected through normally closed contacts 27A of a read-out relay to a source of positive potential. This connection blocks the current flow from the zero cathode so that when the discharge is located on it the current flows to line 22 and fires thyratron 26, By this means whenever the value in the counting tube arrives at or passes through zero the valve 26 fires and the anode voltage falls from a high potential to a much lower voltage. This may occur at any time in the entry time but the carry to the next denomination is delayed until the completion of the entry cycle. A carry is transferred on a line marked " carry out " which is connected to the input of the next higher denomination corresponding to the " carry in " line shown. The " carry in " line is connected through the contact 30A of a cam controlled relay which is picked at zero index time and remains energized as sufficient time to allow carry's in all stages to be effected. Before energization of the carry relay the contact 30A connects the input of the counting valve through resistor 31 to a high potential line so that on transfer of contacts 30A the voltage on the input condenser 32 is suddenly reduced from that of the high potential to that at the anode of the thyratron 26. This causes a negative pulse to be applied to the guide electrodes of the counting valve to step the discharge on one position. At the end of the card cycle the cam-contacts C8 open to cut off the H.T. supply from all the thyratrons 26. The thyratrons 26 are also used to read out the value registered in each tube 12. This is done by scanning the cathodes in turn with a commutator 44. A set of relay contacts 45 connect the junctions between diodes 18 and resistors 19 of each cathode with the corresponding position on the commutator 44. The commutator applies a positive voltage to each position in turn so that the current paths from the cathode to earth line 20 are blocked in turn. When the positive voltage is applied to the position corresponding to the cathode on which the discharge is located a current flows to line 22 and fires thyratron 26 so as to provide a differentially timed pulse at plug socket 40. This is connected by a jack to a magnet 41 recording the read out by punching or printing. If the value in the accumulator is negative the relay contacts 45 transfer so that the cathodes are connected to commutator positions corresponding to complementary values. This means that the cathodes are scanned in the opposite order and the read out is in complementary form. The " real/complement " relay contacts transfer automatically when a negative value is contained in the accumulator. This is done by connecting the relay coil in the anode circuit of a thyratron, similar to thyratron 26 but connected to fire when the value registered in the highest denomination is " 9 " (this indicating a negative value in the accumulator). The " carry out " line of the highest denominaation is connected to the " carry in " of the lowest denomination to effect the round carry " during subtraction. Specification 442,534, (Group VIII], is referred to.