Patent GB-801844-A (GB)
Title: New or improved digital coding and translating apparatus
IPC: H03M1/28
Filed: 1955-03-08
Abstract: 801,844. Analogue to digital converters. GIANNINI & CO., Inc., G. M. March 8, 1955 [March 9, 1954], No. 6815/55. Class 40 (1). The invention relates to digital coding and translating apparatus in which syncopic codes are used, a syncopic code being defined as a digital code in which only one symbol changes at a time when passing between any two consecutive numbers. Translation of each normal (Arabic) decimal digit to the corresponding syncopic decimal digit requires reference to the decimal digit of next higher significance (the preceding digit). Two distinct types of correspondence are used for relating the syncopic decimal symbols and the normal decimal figures which they represent, one type of correspondence being used when the preceding normal decimal digit is even and the other type when that digit is odd. The quality of a number that determines whether it is even or odd is defined as its parity. Each digit of the syncopic decimal code is represented by four or more binary digits, which are directly indicated by the respective states of corresponding two-state devices, the two states being indicated by x and o. In one form of syncopic decimal code each digit may assume ten distinct values, each of which represents one Arabic figure when the preceding Arabic parity is even, and represents another such figure when that parity is odd, each of those two figures being in every instance the complement on nine of the other. When the preceding parity is even the syncopic digit values are identical with the Arabic figures they represent. For example, Arabic number 9 is represented in the syncopic decimal code by 9, and in the syncopic binary code by xooo, xooo, xoox, and Arabic number 10 is represented, in the syncopic decimal code by 19 and in the syncopic binary code by xooo, xxoo, xoox. In this case each decimal digit is represented by four binary digits, xooo representing zero, and the binary code representation of any Arabic digit value for one preceding parity is transformable into the binary representation for the other preceding parity by reversing the state of the last binary digit of the four, the state o being allotted for the syncopic decimal digit values 0 to 4 and the state x for the values 5 to 9. The Specification includes a table showing the preferred code. The syncopic binary code may be generated by a rotary disc provided with commutator formations corresponding to the twelve code elements required to represent three decimal digits distributed on both faces of the disc and co-operating with brush contacts, Figs. 1 to 3 (not shown). Fig. 4 shows a system for converting the syncopic binary code into common Arabic numbers. The brushes from the rotary disc are represented by the connections A ... D at 100X, 100Y and 100Z. Each complementing circuit 134 is required to invert only a single code element when the preceding Arabic parity is odd, but not when it is even, this information being obtained from the parity discriminating circuit 132. The output from each translating circuit 130 is delivered to the appropriate one of ten output terminals. The Y sub-system of Fig. 4 is shown in Fig. 5, the four input connections A ... D being connected via respective relay coils KA, KB, KC and KD1 to a battery 140 so that grounding of one or more of these connections actuates the corresponding relays. Relay KD1 is included in complementing circuit 134Y and through switch contacts S1a, S1b, controls the energization of relay KD2. When the preceding parity is even line 141 is grounded and when it is odd line 142 is grounded, the effect being to invert the state of code element D as regards its control of relay KD2 whenever the preceding parity is odd. In the translator circuit 130Y the relay switches pass a ground connection through one switch only of each of the four relays so that it is supplied to only one of the ten output terminals 138Y according to the energization of relays KA, KB, KC and KD2. In the parity discriminating circuit 132Y a ground connection is passed from the grounded armature S2 of relay KB, through a series of switches to the line 141a whenever the energization of the relays represents an even Arabic figure and to the line 142a whenever an odd Arabic figure is represented. In a modification, Fig. 6 (not shown), additional switch connections provide an indication of incorrect operation. Reference has been directed by the Comptroller to Specification 762,284.