Patent GB-940678-A (GB)
IPC: G06G7/28
Abstract: 940,678. Electric analogue calculating. TECHNION RESEARCH & DEVELOPMENT FOUNDATION Ltd. Aug. 9, 1960 [Sept. 2, 1959], No. 27596/60. Heading G4G. A generator of a continuous function L(x - x i ) which is constant for values of x on one side of x = x i  (a constant) and is a linear function of x on the other side thereof comprises an input circuit feeding an input signal representing (x - x i  ) to the base of a transistor operating at a predetermined emitter current having an emitter resistance connected to a constant potential source developing the required L function at such emitter electrode by driving the transistor into saturation to produce the constant domain of the function and by operating linearly to produce the linear domain having a potentiometer connected to the emitter means enabling the output voltage to be adjusted to represent the required function. Fig. 6 shows a circuit for generation of an L function of x (Fig. 1) given by L(x - x i ) having a constant value for x lying on one side of value x i  and being linearly related to x on the other side thereof. An input voltage V i  = x - x i  where x is variable and x, is a predetermined constant is applied over a parallel RC circuit to the base of PNP transistor 13 whose collector C is grounded and whose emitter E is connected over resistor 15 to a constant positive voltage + V on terminal 14, while adjustable resistance potentiometer 16 is connected between the emitter and constant voltage terminal 17 to derive an output voltage at slider 18. The bias voltages are proportioned so that for (x - x i ) < 0 the transistor is saturated to produce a constant output while for (x - x i ) > 0 it operates as a common collector amplifier to produce a linear output of slope adjustable by potentiometer 16. A reversed L function (Fig. 2) is produced by using a NPN transistor with reversed signs of voltages at 14,17 (Fig. 7 not shown). A high value of resistance 15 is necessary to give a sharp transition between the constant and linear outputs (Fig. 8 not shown) while a small positive bias is applied to terminal 17 and adjusted so that for (x - x i ) < 0 the potentiometer output is minimised to a small positive value. Alternatively, terminal 17 is grounded and a small negative bias is applied to collector C. The slope of the linear part of the L function is alternatively adjustable by arranging the potentiometer to feed input terminal 10. For synthesis of complex functions, an input voltage representing an independent variable x is applied to an impedance converter 21 (Fig. 9) energizing channels A 1 , A 2  . . . . . A n  comprising the circuits of Fig. 6 (or Fig. 7) in parallel at low impedance together with an adjustable constant voltage at 17 from a DC energized adjustable potentiometer (Fig. 11 not shown). The channels produce respective L-function voltages whose slopes and transitions at x i  are individually adjusted, which are connected by changeover switches S 1 , S 2 .....S n  either to sign changing adder 22 or to sign changing adder 23 which also receives the output of 22 together with an adjustable voltage at terminal 25 at which the respective L 1 , L 2 , L 3  ..... L n  functions with transitional points X 1 , X 2 , X 3 .....X n  may be combined in either polarity to produce a voltage representing the required function F(x) (Fig. 3). In a modification (Fig. 10) each L-function channel may be biased at the base of its transistor from potentiometer 41 across equal and opposed direct voltages, which adjusts the transitional point x i . In a further modification (Fig. 12) the returns of the transistor collector and the output potentiometer (Fig. 6) are connected to a variable voltage source proportional to x i  and the input voltage x is applied to the transistor base; the output voltage being elevated by x 1 ; and the respective channel circuits C 1 , C 2  .... C n  (Fig. 13) are energized in parallel over impedance converter 31 from an input voltage representing independent variable X 1  together with adjustabletransition point voltages X 1 , X 2 , X 3 .....X n  from ablock source 33; the latter voltages being combined in sign changing adder 35. The L-function voltages from the respective channel circuits are additively combined at 34 with subtraction of the sum of the transition point voltages and the output at terminal 36 represents the required complex function. The latter may be synthesised by a combination of 2 functions of (x - x i ) (Fig. 4) defined as continuous functions of x, linear for x i  # x # x i+1  and constant outside this interval, which are generated by channels comprising the circuit of Fig. 10 with the anode of limiting diode 42 connected to the transistor base and its cathode returned to an adjustable direct voltage u at terminal 43; the latter determining the x i  transition point and the voltage on 14 determining the x i+1  transition point, while the slope is determined by the setting of potentiometer 16. Alternatively the anode of the limiting diode is connected to the emitter E and its cathode is returned to an adjustable direct voltage u<SP>1</SP> at terminal 45. Fig. 12 may be similarly modified and Z functions may also be generated by so proportioning the circuit parameters of Fig. 10 so that the transistor is driven from saturation through linearity into cut-off by the variations of the input voltage (x - x i ) with output transitions from constancy through linearity into constancy at the required points. Specification 751, 602 is referred to.