Patent GB-791608-A (GB)
Title: Improvements in or relating to error checking system
IPC: G06K5/00
Filed: 1955-12-08
Abstract: 791,608. Electric digital-data-storage apparatus. COX, B., GOLDBERG, J., and KAUTZ, W. H. Dec. 8, 1955 [Oct. 10, 1955], No. 35313/55. Class 106 (1). A system for detecting errors in transferring data comprises means to enter data into one end of a first circuit path, means to store it at that end, means at the other end of the circuit path to receive the data and enter it into one end of a second circuit path, and means to compare data received at the other end of this path with the stored data in order to detect any difference. As described, data is entered on a decimal keyboard 110, Fig. 1, associated with known printing mechanism and fed to a device 112 for conversion to binary " excess-three " code. After translation to serial form in a logical network 114 it is recorded in the data store 116 of a computer, e.g. a magnetic drum. The same data is then read out and staticized in a register 118 from which it is transmitted in parallel to a decoding arrangement 120 which translates the data back into decimal form and applies it to the keyboard 110. An error indicator 122 signals any discrepancy between the data standing in the keyboard and that received from the decoder 120. When data derived from the computer is to be read out of the data store and printed, it is passed through the devices 118 and 120 and actuates by means of solenoids, the appropriate keys in the keyboard 110. This causes the data to be passed through the devices 112 and 114, as in the first case, but operation of a relay 122<SP>1</SP> now directs the serialized signals to a second register 124, the contents of which are then compared by known means 126 with the data standing in register 118 to detect any difference. Keyboard switching. The depression of any key 200, Fig. 2, transfers two switch arms, e.g. 209U, 209D, from upper contacts 209UA, 209DA to lower contacts 209UB, 209DB, and the key is mechanically latched down. The transfer of one of the upper switch arms to its lower contact (say 209UB) breaks a chain running from earth via relay contacts 212 and the corresponding switch arms -UA of all lower keys in that denomination, and connects it through the corresponding one of a series of relays 300 ... 309, Fig. 3, to a +150 volt supply. The lower switch arm which has been depressed by key operation, prepares for the arrival of a signal from the converter 120 which should agree with the depressed key. The signal arrives at the lower contact (e.g. 209DB) and, if the corresponding key has been depressed, completes parallel circuits to earth via a solenoid 209S and an " error " relay 214. The latter closes contacts 216 in a circuit normally completed by the error relays 2141, 21411 of all denominations. Failure to complete this circuit gives rise to an " error " signal and, in the key column at which disagreement occurs the solenoid (e.g. 209S) operates to pull down the key. Actuation of the key does not occur where relay 214 receives current since insufficient voltage is developed across the key solenoid. The solenoids 201S ... 209S also provide for actuating the keys in accordance with data derived from the computer. Some details of the keyboard construction are given in the Specification. Coding and de-coding. As mentioned above, depression of a key causes energization of a corresponding relay 300 ... 309, Fig. 3, in a coding network associated with that order. A pulse generator 320 subsequently supplies signals on the three leads 321, 322, 323, preferably in sequence, whereby, as a result of the closing of contacts A ... F by the energized relay, output signals appear at terminals V ... Z in accordance with the following code The check digit is chosen to make the sum of " ones " an even number in each case. The outputs of the coder are applied to a logical network (Fig. 4, not shown) to form a serial pulse train for feeding to the data store. The reconversion of binary signals to decimal in the de-coder 120 is performed by further networks of relay contacts (Fig. 5, not shown) in which the relays are energized under the control of a flipflop shifting register or staticizer of a known type corresponding to the device 118, Fig. 1. Also at this stage a check circuit verifies that, of the 32 possible combinations of the five input signals, the pattern is in fact one of the ten valid combinations tabulated above. The comparator 126 is of known type. The second register 124 is a flip-flop shifting register like 118 as described, for example, in " Electronics," December 1949, pages 186 to 192. Instead of a single keyboard input, several may be used.