Patent GB-1074624-A (GB)
Title: A differential function generator
Inventor: BAILEY CHRISTOPHER EDMUND GERV
IPC: G06F17/10
Filed: 1963-05-14
Abstract: 1,074,624. Calculating apparatus. SOLAR- 'TRON ELECTRONIC GROUP Ltd. May 13, 1964 [May 14, 1963], No. 19135/63. Heading G4A. A digital function generator for generating the solutions of certain differential equations comprises a number register divided into a more significant and a less significant part and means for reading out the more significant part and adding it (or a number related to it) to or subtracting it (or a number related to it) from the number in the register. The circuit of Fig. 1, with a switch 18 closed and a switch 19 open, is effective to generate a logarithmic function by storing the independent variable x in a register 12 which takes the form of a counter divided into a higher order part 10 and a lower order part 11. The contents of the higher order part 12 is repeatedly read out non-destructively via gates 15, 16 and subtracted (by means not described) from the number in the counter 10 until the contents of the higher order part 12 becomes zero, the number of subtractions required being counted in a counter 14 which at the end of the operation contains the value of the dependent variable y corresponding to the value of x initially in the counter 10. To generate an exponential function, switch 18 is opened and switch 19 is closed, a standard number is entered in the counter 12 and the higher part 12 added repeatedly to the number in the counter 10 until the counter 14, which counts the number of such additions, reaches the value of the independent variable x, when the counter 12 holds the required corresponding dependent variable y = Aexpx, where A is a constant. The circuit of Fig. 1 may also be adapted to form the function z = xy/w where x, y and w are independent variables by subsidiary steps involving generating logarithms and exponentials. By employing a pulse frequency dividing circuit (called a " fractional sealer " or " linear gear-box ") connected to the counter 14 (Fig. 2, not shown), powers and roots of an independent variable may be generated. By employing two interconnected counters 10, trigonometric and hyperbolic functions may be generated (Fig. 4, not shown), and this circuit also may be modified by the provision of a " linear gear-box " effective to multiply pulse rates (Fig. 6, not shown). An application of a sine and cosine function generator to the analysis of the transfer function of an electrical network is described with reference to Fig. 7 (not shown), the network whose transfer function is to be analysed being connected between terminals 53, 54. The input V 2  at 54 is converted to digital form and is applied to linear gear-box multipliers, together with the outputs of a sine-cosine function generator 50, the outputs of the gear-boxes being passed to registers 59, 60 where they accumulate for a predetermined number of cycles of the sine and cosine waves, the results, which represent values in cartesian co-ordinates being displayed at 61, 62. If desired, a conversion to polar co-ordinates can be made by employing a further sine-cosine function generator 65. The counters employed may be binary or binary coded decimal.