Patent GB-856294-A (GB)
Title: Electric code conversion apparatus
IPC: H03M7/00
Filed: 1958-10-13
Abstract: 856,294. Electric code converters. NATIONAL CASH REGISTER CO. Oct. 13, 1958 [Nov. 1, 1957], No. 32549/58. Class 40 (1). A code conversion circuit adapted to receive signals on a combination of input lines in any one of three input codes and produce equivalents on a combination of output lines in a common output code comprises a co-ordinate array of magnetic cores, decoding networks 26, 27 and 28, 29, Fig. 1, by which appropriate column and row conductors are selected by the input signals to switch the core representing the character in the input code being used. Each core may represent in the different input codes one or more characters, there being a separate set of " sensing " lines for each input code, predetermined ones of one or more sets being inductively coupled to each core according to the number of characters represented by the core. Each line of each set is connected to a combination of output lines as is required to represent, in the output code, the character represented by the core selected and switching means is provided for selecting only that set of sensing lines which corresponds to the input code being used. The three input codes F, D and T using six, seven and five binary bits per character are illustrated in part in Fig. 3. A binary " 1 " on an input line I1 to I6 being represented by zero volts and a binary "0" by - 8 volts. Lines I1<SP>1</SP> to I6<SP>1</SP> are complementary to lines I1 to I6, being at zero volts for a binary " 0 " and - 8 volts for a binary " 1." The input data may be derived from punched tape. As shown in Fig. 2, the decoding circuits 26, 27 and 28, 29 are transistor switching networks each having four output lines connected to the sixteen column and row drive lines in groups of four so that by selecting one of the four outputs in each of circuits 26 and 27 one of the sixteen column lines can be selected. One of the row lines is likewise selected by completing a circuit through one of the four output lines of circuits 28, 29. Diodes are included in the connections to the drive lines. If input code D is being used (see Fig. 3) row control switch S2 and column control switch S3 are closed. Cores are designated by column and row number, e.g. 00-05 which corresponds to " I " in code D (and " A " in code F). Switch S2 connects emitters of transistors 75, 76 to earth 67. These transistors are controlled by signals I6 and I6<SP>1</SP> applied to their bases. Switch S3 similarly earths emitters of transistors 71, 72 controlled by signals 171 and 17. Signals I5 and I5<SP>1</SP> control the four output transistors in circuit 28. Signals I4, I4<SP>1</SP>, I3 and I3 control the network in-circuit 27. Signals I2, I2<SP>1</SP>, I1, I1<SP>1</SP> control the network in circuit 29. In the case of character " I " in code D the seventh bit is " 0 " and signal I7 is therefore - 8 v. This causes (PNP) transistor 72 to conduct to select column lines 0, 4, 8 or 12. In circuit 27 (NPN) transistors 88 and 89 are made conductive by signals I3<SP>1</SP> and I4<SP>1</SP>. Transistor 88 is connected to column lines 0, 1, 2 and 3; and when a clock pulse arrives on line C1, therefore, a driving current will pass from earth 74 via switch S3, transistor 72 column line C-00, transistors 88, 89 and 90 to negative source 91. In a similar way row line R-05 is selected through transistors 75, 76, 77, 78 and 79. The core 00-05 at the cross-over point of these lines is switched and in switching produces an output signal on sensing line IF1, Fig. 1. There are three sets of these lines having letters F, D, T respectively and they are taken to transistor amplifiers 41-48. The appropriate set of lines is selected by one of switches S11, S13 and S15 (S13 for code D) to gate the signals via an amplifier to appropriate ones of the output lines I1<SP>11</SP> to I8<SP>11</SP>. Shift characters.-In code F alphabetic characters may be of upper or lower case, the case being indicated by a preceding upper or lower shift character. Similarly in code T shift characters indicate whether the following characters are numbers or letters. Shift characters are entered on the input lines as above and set corresponding cores. For example the upper shift character in code F selects core 08-13 or 09-13 depending upon whether the shift character flip-flop A1 is in one state or the other. The sensing lines coupled to shift character cores are IF9, IF10, IF11 for code F and IT9, IT10 and IT11 for code T. These produce an outputs on lines IC9, IC10 and IC11, the latter two of which set or unset flip-flop A1. For codes F and T, switch S4, Fig. 2, is closed and according to the state of flip-flop A1 transistor 100 or 101 is selected and the column line selected varies correspondingly. The signal IC9 prevents the recording device connected to the code converter from making a recording in response to the shift characters. This signal also appears as the result of a " cancel " code punched in the tape as to delete a character punched in error. A parity check circuit 55 of known kind is connected to lines II<SP>11</SP> to I7<SP>11</SP>, line I8<SP>11</SP> being an indication used in code F that the character, e.g. " a " is of lower ease. If the number of " 1 " bits in any output character is not odd circuit 55 responds and stops the apparatus.