Patent GB-985705-A (GB)
Title: Within-limits comparator
IPC: G11C8/02
Filed: 1963-04-18
Abstract: 985, 705. Digital data storage; recognizing characters. SPERRY RAND CORPORATION. April 18, 1963 [May 1, 1962], No. 15336/63. Headings G4C and G4R. [Also in Division H4] An arrangement for comparing test numbers with a plurality of data words each of which represents a numerical interval comprises means for comparing a test number simultaneously with a plurality of interval-defining words to determine in which interval the test number lies. The arrangement may be applied to character recognition and to radar tracking (see Division H4). As shown in Fig. 1, a plurality of storage registers are arranged in pairs 66, 68. Each storage register registers three number intervals and consists of a single column of a matrix, a binary digit being represented by a pair of elements 10 being in states "0,1" to represent a binary "0" and "1, 0" to represent a binary "1", an element in the "1" state being shown with a cross in Fig. 1. Each element 10 itself consists of two magnetic cores (not shown) as described in U.S.A. Specification 3,015,807. If both elements 10 of a digit-representing pair are in the "0" state, the pair represents an arbitrary digit "b". Thus register 00 of pair 66 in Fig. 1 stores the triplet of number intervals 00111b, 0001bb, 00001b, the number interval 0001bb for instance representing an interval of numbers 000100 to 000111 (i.e. decimal interval 4 to 7 inclusive). Entry of data. To enter the word shown as stored in register 00 of pair 66, the determined digits "0" and "1" of the word are entered in a register 24, the remaining stages of the register corresponding to those where it is desired to store a "b", being supplied arbitrarily with a "0" or "1". Outputs from both true and complementary sides of each stage of the register 24 are applied to a gating and driving circuit 18 employing transistors (Fig. 2, not shown), the gates being enabled via conductors 20 where it is desired to store a "0" or "1", the remaining gates being inhibited corresponding to the storage of a "b". The particular column for storage is selected by conductors 33 connected to driving circuits 32. Comparison operation. A test number to be compared with the data in the storage matrix is entered in the register 24 and corresponding potentials are applied via drivers 18 to the rows of the store. The stages of the store registers which store binary values equal to the value in the corresponding stage of the register 24 produce no output signal on the column sense line coupled thereto, whereas those register stages storing binary values not equal to the corresponding bit of the test word will produce an output. Further, the stages of the storage registers which contain a "b", (i.e. where both elements 10 of a stage contain "0") will produce no output. Thus the only sense line 16-00 to 16-03 which produces no output is that which stores an interval containing the test word. To provide intervals of more general length not necessarily a power of two, two adjacent matrix storage registers such as the pair 66 comprising registers 00 and 01 can be arranged to store adjacent intervals such as 14-15, 16-31 and the sense lines 16-00, 16-01 of these columns can be connected via a single AND gate 42 to an indicator core 58. Control means (not shown) are effective to cause the comparison in turn of the three segments X, Y, Z of the register 24. The cores 58, 60 are "set" at the commencement of the comparison and only the core or cores which remain "set" at the conclusion of the operation correspond to register pairs storing intervals in which all three segments X, Y, Z of the test number are contained. Character recognition. The Specification describes briefly an application to character recognition in which each stored word in the store with "arbitrary" bits in predetermined positions represents a character such as a letter or number. The digitized representation of a sensed character is placed in the register 24 as a test word and the comparison operation performed as described above. An output on a column sense line 16-00 to 16-03 indicates that the word stored in that column corresponds to the sensed character. The output signal produced can be utilized to operate a printer to print the character. Specification 916,909 and U.S.A. Specification 3,070, 783 also are referred to.