Patent GB-961941-A (GB)
Title: Electrical circuits for performing logical operations
IPC: H03K19/177
Filed: 1960-08-18
Abstract: <PICT:0961941/C4-C5/1> <PICT:0961941/C4-C5/2> <PICT:0961941/C4-C5/3> An electrical circuit, which can be printed, for performing logical operations on n binary input variables comprises a plurality of photoconductive switching elements 13-0 &c., Fig. 1, mounted on one side of a glass plate 11 and connected, Fig. 3, in the pattern defining the logical form of the circuit and a plurality of electroluminescent operating elements 12, 18, 19-0 &c. mounted on the other side of the plate 11 in positions corresponding with associated switching elements.  The photo-conductive elements are applied by silk screen printing and sintered.  A network of conductors 15X &c. is printed over the elements.  The operating elements are electroluminescent lamps formed by the layer 12 of conductive material, e.g. tin oxide, the layer 18 of electroluminescent-dielectric material and the electrodes 19-0 &c. The lay-out of the switching elements is shown in Fig. 3, and comprises (n+1) rows of series-connected switching elements, 13-0 &c., arranged in pairs, each of the rows 1 to n corresponding to an associated input variable, one element of each pair being closed when the variable associated with its row is binary digit 1, the other being closed when the associated variable is binary digit 0, the first row consisting of two elements 13X and 13X, each pair of elements of the following (n-1) rows being shunted across one switching element of the immediately preceding row and the (n+1)th row comprising the same number of elements, 13-0 &c., as those, 13<\>bZ-1 &c., in the nth row, a selected one of the (n+1)th row of elements being closed in accordance with the logical operation to be performed by the circuit, in which one end of each row is connected to a common input terminal 16A, 16B and the other end of each row is connected to a common output terminal 16C, whereby a circuit is completed between the input and output terminals when the values of the input variables correspond with the logical function selected by the closure of the corresponding switching element of the (n+1)th row.  The circuit includes a plurality of operator terminals 21A-21N, Fig. 4, each of which is connected to one or more of the electrodes 19-0 &c. so that the logical function of the circuit can be selected by applying a potential to a selected number of the operator terminals.  The conductive layer 12 is connected through terminal 21Q to ground. When it is desired to drive several logic circuits from the output of a preceding logic circuit, each circuit is provided with two outputs representing fulfilment of its function (output 16C) and non-fulfilment (alternative output 16D). For this purpose an inverter 19-40 &c. is connected through terminal 21P to output bus 31 and output terminal 16C causing the inverter to luminesce during each output, illuminating the photo-conductive element 13-40 which connects alternative output 16D to ground. Should the output bus 31 not be conditioned, the pulse is connected via conductor 45, Fig. 3, resistance 25 and conductor 46 to element 13-40 as a terminal and to the alternative output terminal 16D via conductor 41.  The terminals 16A &c. are plugged into a socket 17, Fig. 1, which has terminals connected with other switching circuits shown schematically as input signal generator 61, switches 60 and 62 and output circuit 63.  In a different form of the device the switching elements are superconductors and the operating elements are magnetic field producing elements printed on either side of a glass plate.  In this form the inverter arrangement 19-40 &c. is omitted and two complete interconnected blocks of elements, a true block and an alternative block, each having four tiers of elements, are provided.