Patent GB-663225-A (GB)
Title: Electrical computer
IPC: G06G7/161
Filed: 1949-02-16
Abstract: 663,225. Analogue electric calculating apparatus. HAZELTINE CORPORATION. Feb. 16, 1949 [Masch 2, 1948], No. 4279/49. Class 37. An electrical computor for solving equations involving known and unknown parameters comprises a reference circuit (11) having circuit elements so proportioned as, upon application of an electrical signal thereto, to develop an electrical effect varying as a predetermined time function which, at an instant of time determined by an independent-variable known parameter of the equation to be solved, reaches a value representing the known parameter; a source of potential (34) having a value representative of the independent-variable known parameter; means (31) for utilizing the potential of the source (34) and the said electrical effect to develop a control effect; a controlled circuit (15) having circuit elements so proportioned as, upon application of another electrical signal thereto, to develop another electrical effect having a value electrically independent of the value of the first-mentioned electrical effect and varying as a predetermined time function, a value of which at some time is related to the value of an unknown parameter of the equation; a signal-sampling circuit (33) responsive to the control effect and arranged to determine only the instantaneous value of the other electrical effect, at the predetermined time, to derive a resultant electrical effect which represents the unknown parameter ; and means (54) for utilizing the resultant effect. In a first embodiment a timing pulse generator 18, Fig. 1, produces a series of negative pulses A, Fig. 2, across a resistor 30, which are applied to the grids of tubes 13, 17, rendering the tubes non-conductive from time t1, so that condensers C 1 <SP>1</SP> and C" previously charged up to voltages E 1 <SP>1</SP> and E 1 <SP>11</SP> selected by adjustable batteries 12 and 16, respectively, commence to discharge exponentially (curves B and F) through associated resistors R<SP>1</SP> and E<SP>11</SP>. Meanwhile a selected voltage E 2 <SP>1</SP>, developed across the cathode load resistor 36 of a tube 35, is applied to the anode of a diode 38 which starts to conduct when the voltage E 2 <SP>1</SP> across the resistor R<SP>1</SP> drops just below E 2 <SP>1</SP>, causing a negative pulse across a resistor 37 which is applied through a condenser 39 to a pulse generator 32, initiating a single pulse, the duration of which is determined by the time required for a negative pulse to be reflected from the open end of a delay line 44 back to the control grid of a tube 41. The resulting pulse from the unit 32 is applied from the output winding 45 of a transformer to a sampling circuit 33 comprising a bridge 47-50 which is rendered conductive for the duration of the pulse, whereby the voltage E 2 <SP>11</SP> to which E 1 <SP>11</SP> has fallen at the time t2 appears across the resistor 52 and is read off by a valve voltmeter 54. The time constants of the networks 11 and 15 are related by the equation and equations of the form y=x<SP>n</SP> can be solved by substituting suitable values in the second equation and adjusting the voltages E 1 <SP>1</SP>, E 2 <SP>11</SP>, E 2 <SP>1</SP> accordingly. The scales on which the voltages of the batteries 12, 16 and 34 are read may be compensated to take account of the fact that the voltages across the resistors R<SP>1</SP>, R<SP>11</SP> and 36 at time t1 may be slightly different from the voltages E 1 <SP>1</SP>, E 1 <SP>11</SP> and E 2 <SP>1</SP>. Further compensations may be made to allow for voltage drop across the diode 38, rectifiers 47-50 &c. In a second embodiment, Fig. 3 (not shown) a similar circuit arrangement is used, but the derived voltage E 2 <SP>11</SP> is preset to a desired value, such as unity, and provision is made for adjusting the voltage E 2 <SP>11</SP> to the value necessary to obtain the preset value of E 2 <SP>11</SP>. A third embodiment (Figs. 4 and 5, not shown) is adapted for equations of the form z=xy, i.e. where E 2 <SP>11</SP>=E 1 <SP>11</SP> E 2 <SP>1</SP>. In a fourth embodiment, Figs. 6 and 7 (not shown), the delay circuit includes a rod or strip of magnetostrictive material, as described in Specification 654,902 and 654,903, [both in Group XL (b)], having energy-absorbing clamps at its ends, and the pulse generator is magnetically, and adjustably, coupled to the strip. In a fifth embodiment for performing addition and subtraction, the timing pulse generator 18, Fig. 8, triggers a single-sweep saw-tooth circuit 91. When the saw-tooth reaches the value E 1 <SP>1</SP> of the voltage source 16 a comparison circuit 31<SP>1</SP> delivers a pulse to a univibrator 75 which generates a pulse suitable for energizing another single-sweep saw-tooth circuit 97. If the circuits 91, 97 are arranged to give saw-tooths AA, BB, Fig. 9, of the same slope, the voltage increment in each circuit during the time interval from t1 to t2 is the same; thus E 2 <SP>11</SP>=E 2 <SP>1</SP>- E 1 <SP>1</SP>, and by adjusting switches 103, 104, Fig. 8, additions and subtractions may be performed. In a sixth embodiment, Figs. 10 and 11 (not shown), saw-tooth voltages having different rates of increase are used for multiplying a number by a factor greater or less than unity. In a seventh embodiment (Figs. 12 and 13, not shown) an exponentially decaying voltage and a saw-tooth voltage are used in - x solving equations of the form y=ae b or for finding logarithms. In an eighth embodiment, Figs. 14 and 15 (not shown), a sine-wave ringing generator is employed with a saw-tooth circuit for solving trigonometrical equations.