Patent GB-593728-A (GB)
Title: Improvements in or relating to apparatus for generating electrical impulses
IPC: G06F7/50
Filed: 1944-05-19
Abstract: 593,728. Pulse generating circuits. NATIONAL CASH REGISTER CO. May 19, 1944, No. 31414/46. Convention date, March 20, 1940. Divided out of 593,682, [Group XIX]. [Class 40 (v)] Apparatus for generating sequences of electrical impulses comprises a plurality of electronic devices connected so as to become operative seriatim, one electrode of each device being connected to an output conductor so that the operation of each device produces a potential impulse in the conductor, means being provided for selecting in advance the number of impulses to be generated in each sequence. The embodiment described forms the impulse-generating unit of the adding machine disclosed in Specification 593,682. The electronic devices are gas-filled electricdischarge tubes 121, 128 arranged in two denominational banks, units and tens, each containing nine such tubes (called digit-impulse tubes), the former bank generating impulses on a units output conductor 150 and the latter on a tens output conductor 153. The number of impulses to be omitted in each bank is determined by depressing corresponding keys 62, 86 which are latched by means not shown, the latching means being released at the end of the emission by the energization of electromagnets 261, 262. Each tank is controlled by a respective starting tube 109, 154. After the keys 62, 86, e.g. key 2 in the units and 70 in the tens, have been depressed, the emission is started by closing a starting key 100 whereby a positive potential from a source 91 is applied through a switch 104 closed by the 2 key 62 to a line 160 connected to the grid of the starting tube 109, causing this tube to fire. The positive potential is also applied from the source 91 through a line 144 and to the anode 110 of the starting tube 109 and by switch 143 closed by the depressed 2 key 62 to the anodes 122 of the digit-impulse tubes 121 up to and including that tube corresponding to the value of the depressed key. The firing of the starting tube causes a current impulse to pass through a condenser 117 to the grid 119 of the 1 digitimpulse tube 121. This tube then fires and emits an impulse through a circuit containing a resistance 125 and condenser 135 in parallel into a units output conductor 150. The end point 123 of resistance 125 is connected to the grid of the 2 digit-impulse tube 128 by a switch 164 closed because the 1 key 62 is not depressed. The cathode of the 2 digit-impulse tube is connected to the other end point 124 of the resistance 125. The condenser 135 keeps the points 123, 124 momentarily at. the same voltage and the 2 digit-impulse tube thus does not fire immediately. When, however, a steady flow is established through the 1 digitimpulse tube anode-cathode circuit and the resistance 125, the potential of point 124 and of the cathode 127 of the 2 digit-impulse tube falls and the latter fires. The resulting impulse is passed to the units output conductor 150 to emit an impulse and also to raise the potential of the cathode 120 of the 1 digit-impulse tube to extinguish this tube. The impulse is not, however, transmitted to the 3 digit tube, since the 2 key 62 is down and so switches the impulse to the conductor 152 connected by the switch 191 of the depressed 70 key in the tens denomination to the tens starting tube 154. This tube then fires and causes the successive firing of the first seven tens-digit-impulse tubes. Seven impulses are thus sent to the tens output conductor 153. The eighth tens tube is not, however, fired because the impulse from the seventh tube is diverted by the switch 161 into a line 152 connected to the grid 267 of a control tube 155, a line which thereupon fires to pass current from source 91 through closed starting key 100 and solenoid 149. The latter opens contacts 146 to shut down the generator and closes contacts 147 to energize the solenoids 261, 262 which release the depressed key 2, 70.