Patent GB-682221-A (GB)
Title: Electronic accumulator for use in calculating apparatus
IPC: H03K21/08
Filed: 1950-12-11
Abstract: 682,221. Digital electric calculating-apparatus. NATIONAL CASH REGISTER CO. Dec. 11, 1950 [Dec. 17, 1949], No. 30200/50. Class 106 (i). Each denomination of an electronic accumulator comprises series-connected trigger pairs and a feed-back circuit, from a trigger pair later in the series to a trigger pair earlier in the series, including a rectifier of the semi-conductor type co-operating with an isolating impedance which assists the back impedance of the rectifier in preventing undesired operation of the later trigger pair by potential changes in the circuit of the earlier trigger pair. Each order of the accumulator, e.g. the units order shown, comprises four double-triodes A, B, C and D, each connected in a trigger circuit sensitive to negative pulses applied simultaneously to both grids. Positive input pulses are supplied over a lead 122 from an impulse generator, which may be as described in Specification 682,220, to one grid of a double-triode 220 and, in orders other than the units order, transfer pulses of similar form are applied to the other grid. Each of these pulses produces a negative pulse at the connected anodes of the double-triode 220 which are connected by a lead 277 and over condensers 275, 276 to the grids of the double-triode A. In the initial state, representing zero, only the trigger B is " on," which is represented by the left-hand triode being conducting. The first pulse applied to the trigger A, switches it " on." The second pulse switches the trigger A " off," producing a drop in the potential of the right-hand anode which is connected over condensers 305, 307 to the grids of the trigger B. The latter is thus switched " off " and, by a similar connection to the trigger C, switches it " on." The count proceeds in this fashion so that after the fifth pulse, the triggers A, B and C are " on." The sixth pulse switches the trigger A " off," which in turn switches the trigger B " off," which in its turn switches the trigger C " off." The trigger C is connected to the trigger D in the way that the other triggers are interconnected and consequently the trigger D is switched " on." The resulting conduction in the left-hand triode of the trigger D produces a drop in the potential at a point 314 between two parts 313, 315 of the anode resistance so that a negative pulse is passed over a condenser 355 and a rectifier 356 to the right-hand grid of the trigger C which is thus switched "on" again. The following pulses switch the triggers in the normal way so that, after the ninth pulse, all of the triggers are " on." The tenth pulse switches all of the triggers " off." When the trigger D is switched " off," a drop in potential occurs at a point 320 between two parts 319, 321 of its right-hand anode resistance and this produces a negative pulse, over condenser 345 which is passed by a rectifier 347 to the righthand grid of trigger B. In this way, trigger B is at once switched " on " again so that the order registers zero. The right-hand grid of each of the double-triodes B and C is connected to the left-hand grid over resistances 296, 304 and consequently, the triggers B and C are relatively sensitive to the feed-back pulses applied to their right-hand grids. These pulses may therefore be of low magnitude and may be supplied from the mid-points of the anode resistances of the trigger D. The parts 313, 319 of the anode resistances are thus in series with the rectifiers so that rectifiers of low back-impedance, such as germanium diodes, may be employed without danger of the triggers B and C influencing the trigger D. Transfer arrangements. A transfer pulse produced by the switching " off " of the trigger D is stored by a double-triode trigger pair 375, normally conducting in its right-hand section. The negative pulse produced at the right-hand anode of the trigger D when the order passes from a registration of " 9 " to one of " 0," switches the trigger 375. The impulse generator for use with the accumulator is arranged to emit negative pulses on a line 395, connected to the left-hand grid of the trigger 375, at times between the normal entry pulses, and the negative pulse immediately following the switching of the trigger 375 restores this trigger. The consequent rise in the potential of the left-hand anode produces a positive pulse across a condenser (not shown) connected thereto by a lead 372, which pulse is applied to the right-hand grid of the input tube 220 of the next higher order to add " one " therein. Zeroizing. The accumulator may be re-set by momentarily opening a switch, e.g. 267, in each order to remove the negative bias from the right-hand grids of the triggers A, C and D and the transfer trigger 375 and from the left-hand grid of the trigger B. Output arrangements. Indicating-means E, described in Specification 682,229, may be associated with the accumulator.