Patent GB-625661-A (GB)
Title: Improvements in and relating to electrical computing devices
IPC: G06G7/20
Filed: 1945-11-30
Abstract: 625,661. Electrical computing devices. SPERRY GYROSCOPE CO., Inc. Nov. 30, 1945, No. 32544. Convention date, Nov. 30, 1944. [Class 106 (i)] [Also in Groups XXXVIII and XL (c)] An electrical computing device for providing an electrical output varying as the reciprocal of a predetermined function comprises an amplifier having a negative feedback circuit containing a variable energy transfer device for controlling the feedback ratio so that this is equal to the difference between the numerical value of the function and a constant term equal to the gain of the amplifier. In Fig. 3, a source of energy 36<SP>1</SP> is connected to a two-valve amplifier. A feedback voltage is applied in series with that from source 36<SP>1</SP> by means of the transformer arrangement 70 and 73 coupling the cathode Joad of valve 72 to the input of valve 71. The arrangement is such that the transformer 70 reduces the proportion of output voltage feedback by a factor equal to the gain of the amplifier, so that a positive feedback voltage equal to the net input to the amplifier is provided. The coupling through transformer 73 is made to vary according to the value of the given function, which may, for example, be the angular setting of a telescope 11, which is then mechanically coupled to the variable coupling transformer 73. The feedback voltage from transformer 73 which is also applied in series with that from source 36, is arranged to be in negative phase and is thus proportional to the angular setting of the telescope. If the energy from source 36<SP>1</SP> is constant, the amplifier output is then proportional to the reciprocal of the angular setting of the telescope. If the energy from the source is variable, the output over input ratio may be measured by means of a ratio indicator 99, such as, for example, that described in U.S.A. Specification 2,190,038. An alternative arrangement is described (Fig. 4, not shown), in which the given function is made to control the amount of negative feedback by means of a potentiometer arrangement which is connected across the output through a transformer, and is used in place of the variable coupling transformer. In this case a tapping on the secondary of the transformer is used to provide the relatively fixed positive feedback voltage, in place of the arrangement utilizing transformer 70. Fig. 1 (not shown) describes an arrangement utilizing a potentiometer, the zero negative feedback position of which is slightly displaced relative to the zero position of the telescope, which effectively introduces the constant term equal to the gain of the amplifier. The amplifier output may be made to correspond with the reciprocal of either the angle of displacement, or the sine or cosine of this angle. A simple mechanical arrangement is described (Fig. 2, not shown) for use with the potentiometer arrangement, to provide sine or cosine correspondence. The variable coupling transformer used in the Fig. 3 arrangement may be either of the type in which the coupling varies as the angle of displacement, or as the. sine or cosine of this angle. If desired, the energy of source 36<SP>1</SP> may also be varied, so that the output of the amplifier varies as the product of two functions,