Patent GB-1070415-A (GB)
Title: Electric integrating computer
IPC: G06F7/70
Filed: 1963-12-02
Abstract: 1,070,415. Electric integrating apparatus. CANADIAN PATENTS & DEVELOPMENTS Ltd. Dec. 2, 1963 [Nov. 30, 1962], No. 47486/63. Heading G4A. [Also in Division H3] The integral I = #dx is computed by applying a train of input pulses of constant magnitude and width at a frequency proportional to the rate of change of variable x to a gate circuit 11 (Fig. 1) controlled by a generator of pulses 12 producing opening pulses at random with respect to the input pulse incidence, and such that the probability of the gate being open at a given time is proportional to the variable y. The gate pulse output operates a counter 13, and it is shown that where #x represents equal increments of x and yj is a value of y for the jth increment of x. It is also shown that if the jth input pulse represents the jth increment of x the probability of such pulse passing the gate is Pj<SP>1</SP> = h yj  and for N input pulses the mean E of the number M of pulses passing the gate is so that the approximate value of the integral is given by and the counter indicates a value I<SP>1</SP> for the integral whose expected value is I, where with random error whose standard deviation where (x 2  - x 1 ) is the interval over which the integral is taken. If the input y may swing positive or negative, two gates (Fig. 2, not shown) are provided each receiving the #x input pulses and responsive to the gate pulse generator receiving the y input signal; one gate operating only when y is positive and the other operating only when y is negative, and the counter operating incrementally in response to gate A and decrementally in response to gate B. The device may be utilized for navigational computation of the integrals for determining distances covered by a vehicle along co-ordinate axes; an input pulse is generated once per increment #s of distance travelled, e.g. once per revolution of a log or a speedometer, and analogue voltages cos# or sin# are derived for the gate pulse generator input from a resolver driven from a direction indicator. The gate pulse generator should operate at a frequency greatly in excess of the occurrence frequency of the input pulses, the gate pulse width as a fraction of the gate pulse period is made equal to the probability proportional to the y input, and gating is effected on the leading edge of the input pulse; the pulse being transmitted if the leading edge coincides with a gating pulse and being arrested if it does not (Fig. 3, not shown). For evaluation of the integral #uvdx, #x input pulses are applied to a counter through a gate, which is controlled by an AND gate responsive to the outputs of gate pulse generators respectively excited by input signals u, v of unchanging sign (Fig. 5, not shown). When u, v may have both positive and negative signs they are applied respectively to gate pulse generators A, B (Fig. 6) to produce for u + a series of pulses of width corresponding to probability P A1 , proportional to u, and for u - a series of pulses of width corresponding to probability P A2  proportional to | u | . Similarly, for v + a series of pulses corresponding to probability P B1  proportional to v, and for v - a series of pulses corresponding to probability P B2  proportional to v | are produced. These are combined in gates 15, 16 so that gate 15 produces pulses of width corresponding to probability P 1  = P A1 P B1  + P A2 P B2  and gate 16 produces pulses of width corresponding to probability P 2  = P A1 P B2  + P A2 P B1 . The input #x pulses are fed to gates 11, 12 respectively receiving the output pulses of gates 15, 16 corresponding to P 1  and P 2 . The simultaneous presence in gate 11 of a pulse of width corresponding to P 1  and the leading edge of a #x pulse increments counter 13 by 1 unit, while the presence in gate 12 of a pulse of width corresponding to P 2  and the leading edge of a #x pulse decrements it by 1 unit, and it is shown that the reading of the counter represents the required integral if the gate pulses representing the two variables are statistically independent. For evaluation of the integral gate pulse generators A, B (Fig. 7) produce pulses of width s corresponding to probabilities P A , P B  proportional to u,v which are applied to AND gates 1, 2 driven from oscillator 18 to operate alternately for time fractions P E  and ( 1 - P E ) so that their outputs are mutually exclusive and are combined in OR gate 17, whose output is thus P A .P E  + P B (1 - P E ) to control gate 11 receiving the input #x pulses. It is shown that the expected value Em of the reading of counter 13 is given by so that for appropriate values of K 1 , K 2 , P E  I #(an + bv)dx. For evaluation of integral I = #1/y, the input #x pulses are applied to turn on a flipflop which is turned off by pulses from a gate circuit receiving pulses from the gate pulse generator responsive to input y. The flip-flop controls an oscillator to generate pulses only when the flip-flop is on, which pulses are applied to the counter and also to the gate. When in the latter the leading edge of an oscillator pulse coincides with a gate pulse and the output of the gate turns off the flip-flop and the oscillator until arrival of the next #x input pulse, so that the number of output pulses is inversely proportional to the probability of a pulse passing the gate; and since the gate pulse generator produces pulses at constant frequency of width proportional to y, the counter indication approximates to the required integral (Fig. 8, not shown). The circuit is applicable (Fig. 9, not shown) to computation of mass m of gas passing a measuring station at pressure P and absolute temperature T where and a #x pulse is generated once per turn of a rotor in the gas flow to represent an incremental distance of gas travel. The gate pulse generator may comprise a transistorized circuit comparing the input voltage with a linear triangular sweep voltage derived from a transistorised generator, and the gate circuit may comprise directly coupled transistorized logic circuits (Figs. 12, 13, 14, not shown).