Electronic circuit for activating an electric lock
United States Patent Perry Apr. s, 1975 AN ELECTRIC LOCK 3.754.164 8/1973 Zorzy 317/134 [75] Inventor: Richard Frederick Perry, London, Primary Miller England Assistant Examiner-Harry E. Moose, Jr. 1 Attorney, Agent, or FirmBrown, Murray, Flick &amp; [73] Assignee: Keith James Goss, London, peckham England; a part interest [22] Filed: Nov. 12, 1973 [57] ABSTRACT [21] Appl&#39; An electronic circuit is provided for operating an elec- 1 tric lock. The circuit is activated by switching a pre- [52] US. Cl 317/134; 70/278 selected combination of switches in a pre-selected se- [51 1 Int. Cl E05b 49/00 quence. Any number of switches may be provided and [58] Field of Search 317/134; 340/63, 64, 147 R, there may be more switches than switches forming the 340/147 CN, 147 MD, 149 R, 149 A, 164 R, pre-selected combination. Furthermore, circuitry may 164 A, 164 B; 70/277, 278; 307/10 AT be provided such that the circuit is only activated if each switch is switched within a pre-selected time [56] References Cited delay of the switching of the preceding switch.  
  UNITED STATES PATENTS 8 Claims, 5 Drawing Figures 3.633.167 1/1972 Hedin 317/134 SIX 52X 53X SLX 55X SEX MSl QB MS2 M53 QB MSL QB M55 TO 0R3 R Q T0 LOCK M56 g) M57 VIA RELAY S7X FROM M s 8 as Q 0R1 o/p w PATENTEU 81975 87 5,913  
 NOR  
 NOR  
 &amp;  
 NOR  
 NOR  
 NOR  
 PATENTEDAPR 8|975 sum u o 4 COUNTER A C D &#39;8 TO NOR3 RMSI&#39; ELECTRONICVCIRICUIT FOR ACTIVATING AN ELECTRIC LOCK This invention relates to an electronic circuit for activating an electric lock.  
  Conventional locks require the easier-to-carry key which is inconvenient and may be lost, allowing illegal entry into premises protected by the lock. Combination locks are mechanical devices and do not provide a very secure protection.  
  This invention is intended to provide a lock having a high degree of security which overcomes the disadvantages of the previously known systems.  
  According to the present invention there is provided an electronic circuit for operating an electric lock comprising an array of switches and logic circuitry connected to at least some of the switches, the circuit being activated when a pre-selected combination of the switches is switched in a pre-selected sequence.  
  The switches may be push-button switches or any other suitable form of switches such as proximity switches.  
  The circuit may also comprise delay circuitry connected between the switches and arranged such that the circuit is only activated when the switches of the combination are switched in sequence with a preselected time delay between each switching operation.  
  The electronic circuit may also comprise additional logic circuitry for preventing the activation of the lock if incorrect switches are switched or are switched out of sequence.  
  An alarm may also be provided to give an indication of a person attempting illegal entry when a wrong combination is switched.  
  The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which FIG. 1 is a block diagram of an electronic circuit for activating an electric lock;  
  FIG. 2 is a block diagram ofa safety system for incorporation into the circuit;  
  FIG. 3 is a block diagram of an alarm system for incorporation into the circuit;  
  FIG. 4 is an alternative circuit for activating an electric lock; and  
 FIG. 5 is a modification of FIG. 4.  
  The electronic circuit comprises 12 push-button switches of which 7, SlX to 57X, are shown in FIG. 1. Each of switches SIX to 57X is connected to a first input of respective NOR gates NORl to 7..The outputs of NOR gates l to 6 are connected to inputs of respective monostable multivibrators MSl to MSS whose QBar outputs are connected to the second inputs of the following NOR gates. The second input of the first NOR gate is connected to earth. The Q output of monostable multivibrator M86 is connected to a first input of AND gate 1 having a second input connected to the 0801&#39; output of a multivibrator M88 and a third pea&#39;ted up to the pressing of switch 5X6. Each switch must therefore be pressed within 2 seconds for example, of the pressing of the preceding switch. After the depressing of 5X6, the Q output of multivibrator M86 is in the HIGH condition for 2 seconds and providing the monostable M58 has not been triggered, (the function of M88 will be described later) the pressing of SX7 within the prescribed time of 2 seconds will open the AND gate to trigger the lock monostable multivibrator MS7. With this triggered the electric lock is activated for the duration of the pulse width of monostable multivibrator 7 which, for example, could be 5 seconds.  
  The circuit shown in FIG. 2 is a safety circuit which closes the AND gate 1 if a wrong combination of pushbuttons is pressed. The first NOR gate 7 has its inputs connected to S1 and S2 and the second NOR gate 8 has its inputs connected to S2 and S3 and so on, until the last NOR gate NOR12 which has its inputs connected to S6 and S1. The .NOR gates 7 and 8 have their outputs connected to the inputs of an OR gate 13 and similarly NOR gates 11 and 12 have their outputs connected to the inputs of an OR gate 14. NOR gates 9 and 10 have their outputs connected to inputs of OR gates 15 and 16 whose other inputs are connected to the outputs of OR gates 13 and 14. The outputs of OR gates 15 and 16 are connected to OR gate 1 whose output is connected to the input of the monostable vibrator MS8.  
  If S1 to S6 are pressed simultaneously the NOR gates and OR gates are activated which in turn trigger the monostable multivibrator M88 whose QBar input goes LOW to prevent the AND gate 1 from opening and thus the electric lock from being operated. M88 is also triggered if any of the combinations S1 and S2, S2 and S3, or S3 and S4, S4 and S5, S5 and S6, or S6 and S1 are pressed together. Therefore, the only method of activating the electric lock is to press the correct combination, one button at a time and within the predetermined time limit. The circuit can also be arranged so that the triggering of the safety monostable triggers the alarm system.  
  The circuit shown in FIG. 3 provides for an alarm to be triggered under certain conditions. The electronic circuit as has been stated, has 12 push-button switches of which 7 are connected to the NOR gates in FIG. 1. The switches S2 to S7 are preferably double pole switches having their second poles arranged as shown in FIG. 3 and the remaining switches which are not used in the combination may just be single pole switches S8Y to SBY. The second poles of the switches S2Y to S7Y and the switches S8Y to SBY are connected to the inputs of a Counter 17 which unless earthed by the closure of one of the switches S2Y to SBY is held at a HIGH voltage by resistor 18. Outputs AB and C of the Counter are connected to inputs of a NAND gate 19 whose output is connected to the first input of a NOR gate 20 having a second input connected to the output D of the Counter 17. The output of the NOR gate 20 is connected to the input of an AND gate 21 connected to the QBar output of the monostable multivibrator 7. The output of the AND gate 21 is connected to the input of an OR gate 22 having a second input connected to the output of the OR gate 1 of the safety circuit shown in FIG. 2. The output of the OR gate 22 is connected to the input of the monostable multivibrator MS9 whose Q output is connected to an alarm via a relay system. The Q output of the monostable multivibrator 9 is also connected to the input of an OR gate 23 having a second input connected to the Q o utput of the monostable multivibrator M87 and a third input connected to the output of the NOR gate 1 of the switch SIX. The output of the OR gate 23 is connected to the Reset input of the Counter 17.  
  If any of switches S2Y to SBY are pressed a total of 7 times without S1 being pressed, the counter counts up to 7 giving outputs 1 l 1 and on the lines A B C and D. In this case if MS7 has been triggered, the AND gate 21 triggers the alarm monostable MS9 which in turn activates the alarm. Alternatively, if OR gate 22 has an input from OR gate 1 from the safety system, the monostable MS9 is also triggered. The counter can be reset by the pressing of the switch S1, the triggering of the monostable M87, or the triggering of the alarm monostable MS9.  
  The circuit of FIG. 1 allows for any combination of numbers to activate the alarm including repetition of numbers, providing they are not adjacent combinations. For example, the circuit of FIG. 1 could be arranged to activate the lock when the switches S1,2,l, 3,1,4, 1, were activated in that order and this is simply arranged by connecting the switch input wires of NOR3, NORS, and NOR7 to the switch input of NORl.  
  However, the circuit of FIG. 1 does not allow for successive repetitions of digits, such as in the combination 1 l 2 3 4 5 6, for example. Successive repetitions are catered for by the circuit shown in FIG. 4. The switch S1 is connected as before to a first input of NOR gate 1 whose output is connected to multivibrator MS]. The switch S1 is also connected to the input of a Counter whose Reset input is connected to QBar output of mu]- tivibrator MSl. A C and D outputs of the Counter 24 are connected to the inputs of the NOR gate 25 whose output is connected to the input of the NAND gate 26 having a second input connected to the B output of the Counter 24. The output of the NAND gate 26 is then connected to the input of the NOR gate 2 whose second input is connected to the switch S2 having output at the NOR gate 2 is connected to the monostable multivibrator MS2 as before.  
  Pressing S1 for the first time triggers MSI, which in turn enables the Counter for the duration of the pulse width of MSI. Releasing S1 gives a positive going edge at the counter input so that the counter now registers that S1 has been pressed once. S1 must now be pressed and released again followed by S2, before the counter ,is reset by the rising edge of the M81 output, to enable the signal to proceed to the NOR3 input.  
  In this manner any digit may be repeated successively any number of times by suitable decoding of the counter outputs.  
  An alternative method of achieving this repetition of digits, is to use a retriggerable monostable multivibrator RMSl, which eliminates the need for a counter. This is achieved by using a suitable pulse width for the retriggerable monostable multivibrator RMSl. The pulse width is chosen such that the switch S2 cannot possibly be pressed in time to allow the signal through to NOR3, unless S1 has been pressed a sufficient number oftimes. This is&#39;because every subsequent activation of S1 extends the pulse width of RMSl by an amount equal to the orginal pulse width.  
  Returning for the moment to FIG. 3, it can be seen that if SA, for example, is held down then the counter will not register any subsequent presses. In this way the alarm system could be eliminated. This problem could be, however overcome by extending the combinations of double presses which are recognized by the safety system shown in FIG. 2.  
  The electronic circuit can be used to activate any kind of electric lock. It can be used for example with car ignition systems. The electronic circuit has two main advantages. Firstly no key is required, and secondly with suitable monostable pulse widths, the lock can serve as&#39;a reaction test so that if the combination was not completed quickly enough, the lock would not open. The electronic circuit may be used in conjunction with any other entry system.  
  In the example, 12 push-buttons were used out of which 7 formed the combination. However, any number of push-buttons can be used and any number of these can be used to provide the combinations. There are therefore a very large number of combinations that can be formed out of such a system.  
 I claim:  
  1. An electronic circuit for operating an electric lock comprising an array of switches, at least some of said switches forming a pre-selected combination, logic circuitry having a series of logic gates connected to said switches forming said pre-selected combination, and delay circuitry connected between the switches forming said combination, whereby said circuit is only activated when the switches of the combination are switched in a pre-selected sequence within a preselected time delay, said delay circuitry including a series of monostable multivibrators having a predetermined pulse width, the monostable multivibrators being connected between the output of one logic gate and an input of a following logic gate, except for the output of the last but one logic gate which is connected through a monostable multivibrator to the input of an AND gate whose output is connected to the input of a further monostable multivibrator whose output is connected to a relay for operating said lock, a second input of said AND gate being connected to said last switch of said combination through a logic gate.  
  2. The circuit of claim 1 in which said logic gates connected to said switches are NOR gates, and the QBar outputs of said monostable multivibrators are connected to the inputs of said NOR gates except for the multivibrator connected to the last but one NOR gate, said multivibrator having its Q output connected to an input of said AND gate.  
  3. The electronic circuit of claim 2 comprising additional logic gates connected to at least some of said switches forming said combination, said additional logic gates producing an output when selected combinations of said switches are switched simultaneously, said output being arranged to deactivate the electronic circuit.  
  4. The electronic circuit of claim 3 in which the switches of said combination apart from said first switch are double pole switches, and wherein the circuit comprises a counter, means for decoding the output of said counter, and means for activating an alarm, whereby said alarm is activated when said switches are pressed a number of times equal to the number of digits in said pre-selected combinations.  
  5. The electronic circuit of claim 4 in which the output of said additional logic gates for indicating when selected combinations of said switches are switched siproviding an output when a switch of the combination is pressed a pre-selected number of times, said counter thus providing consecutive repetitions of digits in said combinations.  
  8. The electronic circuit of claim 6 comprising a retriggerable monostable multivibrator between adjacent logic gates connected to adjacent switches of said combinations, the pulse width of said retriggerable monostable multivibrators being chosen such that the following gate cannot be opened unless the preceding switch is switched the requisite number of times.