Patent GB-665612-A (GB)
Title: Improvements in or relating to calculating machines
IPC: G06F7/498
Filed: 1948-08-09
Abstract: 665,612. Digital electric calculating-apparatus. BRITISH TABULATING MACHINE CO., Ltd. Aug. 9, 1948 [Aug. 13, 1947], No. 20977/48. Class 106 (i). An electronic counter comprises for each order, a series of bi-stable electronic devices selectively settable to represent in combination the values of that order and circuits for coupling said devices for descending count sequence of changes in the value represented in response to successive pulses at the input of the counter, each' pulse corresponding to unit value. Trigger circuits. As described, each stage comprises a trigger circuit T of the type disclosed in Specification 609,502. Each cir. cuit T includes two triode valves so connected that one is conducting while the other is not. Negative pulses applied to points a and h, which are capacitycoupled to the grids of the valves respectively, each reverse the state of the circuit, which is said to be " on " when the left-hand valve is conducting. The anode f of the other valve is then at high potential while its own anode e and a point d in its anode resistance are at low potentials. Entry of minuend. Each decimal order of the apparatus comprises trigger circuits T1, T2, T4 and T8 which when in the " on " state, manifest the values 2<SP>0</SP>, 2<SP>1</SP>, 2<SP>2</SP> and 2<SP>3</SP> respectively. Associated with each trigger circuit, Fig. 3a, are two pentodes P, S and a triode V. To cause the corresponding trigger circuit to assume the " on " state to manifest its corresponding value, a line L, connected to the control grids of the pentode P and triode V is connected to a high potential. The valve V then conducts and, since its anode is coupled to the control grid of the pentode S, the potential of the latter is lowered. The pentodes P and S are thus conditioned and de-conditioned respectively so that, when a high potential is applied through a line 25 to their suppressor grids, the pentode P only conducts. The anodes of the pentodes P and S are respectively connected to points c and f of the trigger circuit so that their respective low and high potentials switch the circuit " on ". If the line L is not connected to a high potential, the triode V does not conduct and so the pentode S, but not the pentode P, is conditioned to conduct, when the potential of the line 25 is raised, to ensure that the trigger circuit remains " off " irrespective of the state of the other trigger circuits to which it is connected. To ensure the ineffectiveness of the valves X and W (see below), during the entry of a minuend, the potential of a line 22u, to which their control and suppressor grids respectively are connected, is dropped by a triode K, the anode of which is also connected to the line 22u, rendered conducting by the high potential on the line 25 to which its grid is resistancecoupled. Subtractive counting. The input line 21 and the points d of circuits T1 and T2 are connected respectively to the points a and h of circuits T1, T2 and T4. The point d of circuit T4 is connected to the point a of circuit T8. Assuming that the four stages of the order are " off," the first pulse applied to the input line 21 must switch the trigger circuit T8 " on " in addition to the trigger circuit T1. For this purpose, a pentode W has its suppressor grid connected to a line 22u to which the anodes of triodes 11, 12, 14 and 18 are also connected. The grids of these triodes are resistancecoupled to the points f of their respective trigger circuits and so when, and only when, each circuit is " off," none of these triodes will be conducting and the line 22u will be at high potential and will condition the pentode W. The control grid of the latter is resistancecapacity coupled to the point f of the circuit T1 so that when the latter is switched " on," the previously conditioned pentode W conducts. A point in the anode lead of the pentode W is connected to the point h of the circuit T8 and so the drop in potential switches this circuit " on ". To ensure the conduction of the pentode W, before it is de-conditioned by conduction in the triode 11, the grid of the latter may be coupled through a resistance R1 and capacity C1 to the point c of the circuit T1 to delay the commencement of conduction. To prevent the circuit T2 switching on " when the order-registration changes from " 0 " to " 9," the point f of the circuit T2 is connected to the anode of a triode X, the grid of which is connected to the line 22u. Thus, as the registration changes from " 0 " the triode X is conducting and so its low anode potential locks the circuit T2 " off ". The second pulse applied to the input line 21 switches the circuit T1 " off ". The third pulse switches " on " the circuits T1, T2, which are no longer locked since the triode X is no longer conducting, and T4 to register " 7 ". The following pulses result in the registration of the numbers " 6 " down to " 0 " in turn since the switching of a circuit on " reverses the state of the next circuit but the switching of a circuit " off " does not. In a modification, Fig. 4, the control and suppressor grids of valves X and W respectively are coupled to the point f of an auxiliary trigger circuit TA, the points a and h of which are respectively connected to the anode leads of two pentodes 91, 92. The control grids of the latter are coupled to the point c of the circuit T1 so that the pentodes are conditioned when the circuit T1 is not conducting. The suppressor grid of the pentode 92 is coupled to the anode lead 22 of triodes I2, I4 and I8, there being no triode I1 in this arrangement, and so when all the circuits are " off," the pentode 92 conducts and causes the circuit TA to be "on " which, in turn, causes the triode X to be conducting and conditions the pentode W to conduct when the potential of its suppressor grid is raised as the circuit T1 is switched on. The suppressor grid of the pentode 91 is coupled to the point f of the circuit T8 so that when T1 is switched " off " but T8 remains " on," the pentode 91 conducts and the circuit TA is switched " off " until " 0 " is registered again. Transfer. The point d of the circuit T8 is connected to the input line of the next higher order so that when T8 is switched " on," i.e. when the registration changes from " 0 " to " 9," a negative pulse is passed thereto. Zero remainder signal. In apparatus having two orders the anode lines 22 of the triodes I of the two orders are resistance-capacity coupled respectively to the control and suppressor grids of a pentode (not shown) which thus conducts when the registration in both orders is zero.