Patent GB-1256730-A (GB)
IPC: E05B45/06
Filed: 1969-12-17
Abstract: 1,256,730. Combination locks. NORTH AMERICAN RESEARCH CORP. 17 Dec., 1969 [15 Jan., 1969], No. 61505/69. Heading E2A. [Also in Divisions G4 and G6] An electronic combination switching device comprises a shift register 30, means for entering random bits into the register, gates 40-54 connected to certain stages of the register to give an output on one of a number of leads manually operable switches S40-S54 being connected to the leads, the arrangement being such that of the switch corresponding to the marked lead is closed. An output is provided to means serving to actuate the switching device. Initially a press-button switch 20 is closed to trigger a single-shot 22. This opens gate 26 and starts a random bit generator 28. The random sequence of pulses enters register 30 until single shot 22 resets leaving a random group of bits in the register. Each stage of the register is connected to an indicator lamp, numbered to correspond with the stage. The secret combination of the circuit shown is 517 outputs from these stages only being connected in the gates in all possible combinations. When a bit pattern as indicated by the lamps is in the register, an output will be given by gate 52 labelled -++, 5 being off and 1 and 7 being on. An operator knowing the combination observes from the lamps which of the combination numbers are on and which off and actuates the corresponding switch. The switches are marked with the combinations of + and - which they represent. When the correct switch is closed a signal passes to counter 58, which counts the correct selections, and to the reset input of a two-stage alarm counter 60. The switches are individually ganged to switch 68 so that when a switch is operated switch 68 closes to retrigger single shot 22 which reenergises the generator 28 and re-opens gate 26 for a brief interval to change the contents of register 30. The operator then operates the appropriate switch as before and a further correct selection signal enters counter 58. The operation is repeated until the counter reaches a predetermined count e.g. a count of five when a signal is given an output 74 to actuate a control relay or a lock mechanism. If an incorrect selection is made counter 58 is reset and a pulse enters counter 60 which after three incorrect selections gives an alarm signal an output 78. Two such systems may be connected together, the first system having one combination, to be operated by a first person and the second a different combination, to be operated by a second person. The outputs 74 are then gated together so that a final control output is obtained only if both system have been correctly operated. The device to be controlled may be at a remote point. Alternatively the display lamps may be at a remote point, operation of the lock could only be effected by contacting the person having custody of the display. The switches could be placed at a different remote point. Instead of the matrix of interconnections 38 there is provided a card insert station comprising a slot to receive an identification card and an array of brushes making contact through holes in the card to make the necessary interconnections between preselected stages of the register and the gates 36. In another embodiment the outputs from the-preselected stages of the register are connected to two way selector switches 94, 96, 98 Fig. 6. The operator moves the three selector switches to one or the other position according to the indicated bits in the register. The switch outputs are connected to an AND gate 100 which has an output only if all the switches are in the correct position. The switch outputs may also be connected through inverters 104 to AND gate 106 so that if an operator is being forced to operate the lock, he may operate all the switches in reverse thereby giving an output from gate 106. This opens the lock but also gives an alarm through OR gate 110.