Coded Electrical Locking Device

Abstract

An electrical circuit for restricting the application of electrical power to an automobile ignition circuit or for controlling other electro-mechanical locking devices wherein a plurality of switches are actuated by a numbered keyboard according to a preselected code so that they must be actuated in proper sequence to unlock the mechanism. The primary code sequence can be changed using the same keyboard to set up a simpler, alternate sequence without the necessity for any electrical or mechanical variations in the device, so that access is permitted by others for limited purposes without the necessity of disclosing the entire code to anyone. The circuit also includes a time delay mechanism which disables the circuit if the proper code sequence is not followed or is not performed within a predetermined period of time.

Description

BACKGROUND OF THE INVENTION

In recent years considerable attention has been directed toward the problem of auto theft and so many solutions have been proposed that it would be exceedingly burdensom to outline them here, even in a general way. Suffice to say that over and above the mechanical locking devices actuated by the ignition key or the like, electrical locking devices have been proposed including ones which provide alarms and even including ones requiring knowledge of a combination or code in order to activate the ignition system. It is recognized by some that the key actuated ignition switch is an inherently weak link in any security system. Thus, various electrical or electronic locks have been proposed some of which include a keyboard controlled circuit thus providing a code or combination electrical lock. While it is reasonable to suppose that an automobile owner could use such a device without difficulty and could remember his combination number, the difficulties with such known devices include the problem of disclosing the combination if the automobile owner leaves it in a parking lot, garage or service station. Thus, none of the previously known devices has provided a satisfactory method for solving this problem. Although some have a changeable code sequence, they all require extensive changes or adjustments in the mechanical or electrical elements of the system which cannot be readily performed by the average user, which require at least partial disassembly or which require considerable time to perform and, being an inconvenience, would probably not be used at all. Yet, the problem of disclosing one's combination is a serious one.

Another difficulty with these prior devices has been that a prospective thief may manipulate the buttons for a sufficient period of time until he stumbles across the correct number. Some devices have an alarm to be actuated if an incorrect number sequence is used but this is a serious drawback for the above-mentioned situation in which the car is left at a service station. Essentially then, the problem which the prior art has failed to solve is how can one provide an electrically encoded locking device having a combination which can be known only to a single person yet which will permit the use of the vehicle by authorized persons through the use of the same locking device and without the inconvenience or annoyance of accidentally actuating any alarm devices, while at the same time presenting to a prospective thief a locking device which is extremely difficult and time consuming to decode.

SUMMARY OF THE INVENTION

I have solved the aforementioned difficulties by providing a keyboard actuated system which may be appropriately encoded as desired with a preselected code sequence, preferably of three or more digits. I have included in my system a time delay mechanism which can be of either of two types. The first type is of the open type, providing a preselected period of time in which the operator is permitted to despress the proper buttons. If he fails to do this in the alloted time, the circuit is disabled for a period of time after which he may try again. The second is a closed type device which gives the operator all the time he needs if he knows the proper combination, but if he depresses an incorrect button or even a correct button out of sequence, the circuit is disabled for a preselected period of time. In addition to deterring propsective auto thieves, the time delay mechanism may also help to discourage use of a vehicle by someone under the influence of alcohol or drugs.

In order to permit the use of the vehicle by authorized persons for parking or servicing without disclosing to anyone the primary code sequence, I have provided a means for substituting a temporary alternate code sequence through the operation of the same keyboard so that no physical changes or adjustments need be made. In one embodiment of my mechanism this alternate code sequence consists of the last digit of the primary sequence plus a fixed, preselected digit not an element of the primary sequence. In a second embodiment of my mechanism I again store all but the last digit of the primary sequence, but I have provided means for selectively adding any one of the unused digits that the operator may select. As another embodiment, the system can store the primary code enabling the ignition system to be controlled by the ignition switch only. In either case, the latching mechanism also disables the time delay circuit making it easier for a parking lot attendant, for example, to operate the vehicle without unnecessary inconvenience.

While the principal discussion contained herein is directed to the application of my locking mechanism to automobile ignition systems, it will be obvious that this new locking system has equal utility in many other types of installations. It is foreseeable that the system might have application to other systems requiring latching or unlatching functions, or limited or sequential access, the varieties of which will occur readily to those skilled in the art. In addition, parts of the ensuing discussion describe various circuit elements, principally for ease of description and it is contemplated that dependable equivalents such as solid state components may be substituted.

It is a principal object, therefore, of the present invention to provide an improved electrically encoded locking mechanism whcih is both simple for the owner thereof to operate but which also permits simple and convenient use thereof by other authorized persons without disclosure of the primary code sequence.

It is another object of the present invention to provide an improved locking mechanism having a secret code sequence which can be conveniently used both by the owner and by other authorized persons yet which is difficult and time consuming for others to decode.

It is also an object of the present invention to provide an improved locking mechanism for automobile ignition systems and the like, which is not only convenient to use, but economical to manufacture yet provides a high degree of security for the owner.

These and other objects of the present invention as well as modifications of the basic circuitry disclosed herein will be readily apparent to those skilled in the art upon reading the ensuing detailed description thereof in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a coded locking device incorporating the basic principles of the present invention.

FIG. 2 is a schematic circuit diagram of a first embodiment of the present invention which incorporates a fixed alternate code sequence.

FIG. 3 is a schematic circuit diagram of a second embodiment of the present invention incorporating a selectable alternate code sequence.

DESCRIPTION OF THE INVENTION

Turning first to FIG. 1, a generalized description of the invention is presented. The actual circuits and their functions are interpreted, as will later become apparent, but the system may be said to be comprised of code selectors 10, preferably in the form of a series of switches, buttons or the like, in a keyboard layout appropriately indexed with letters, numbers or other symbols. The code selectors are coupled through line 11, and ignition switch 13, to a source of electrical potential. The outputs from all but one of the individual code selectors are coupled through line 12 to the primary code 14. A latching mechanism 16 which also includes selector switches which may be part of the keyboard, is coupled directly through line 17 to the source of electrical potential and provides on one of its output lines 18 an enabling signal to a time delay circuit 20. The time delay circuit 20 is coupled through line 22 to the primary code 14.

The other outputs of latch 16 are coupled through line 23 to the primary code 14 and through line 24 to the alternate code 26. A second output from the code selectors 10, which may be coupled to at least one of the selector switches or the ignition switch, is coupled through line 27 to the alternate code 26. The outputs of the primary code 14 and the alternate code 26 are coupled through lines 28 and 29 respectively to an "OR" circuit 30, the output of which is coupled through line 31 to an ignition enable circuit 32 which provides an output 33 to the ignition system or to any other electro-mechanical device to which the system will be attached.

In order to provide an output at 33, through the use of the primary code 14, numbered buttons in the code selectors 10 are actuated providing an output on line 12. As soon as power is supplied to the system through lines 11 and 17, power will be supplied through latch 16 and line 18 to the time delay circuit 20. A fixed time delay is provided in 20 which may, upon expiration of the predetermined time, provide a DISABLE signal on line 22 to the primary code circuits 14 to disable the operation of those code circuits. Thus, if the proper code buttons are not selected within the period of time established by time delay 20, or if an incorrect button is depressed, the primary code will be disabled for a second predetermined period of time, upon the expiration of which the operator may again try to depress the numbered buttons in the proper sequence. When he has done so, an output will produce on line 28 to the "OR" circuit 30 to actuate the ignition enable circuit 32 to provide the desired output. Additionally, if code selectors 10 are actuated which do not correspond to the preselected primary code sequence, the primary code is disabled. As an alternative, use of the wrong code selectors may actuate time delay 20 disabling the primary code for a period of time. Once the ignition circuit is enabled, it remains so until turned off. Therefore, the operator can restart a stalled engine using just a starter switch without having to execute the code sequence each time.

If it is desired to permit others to utilize the system to which this locking device is attached without disclosing to them the proper sequence of the primary code, then code latch 16 is actuated providing outputs on lines 23 and 24. The output on line 23 will provide power to the primary code 14, following which the operator will actuate the numbered buttons corresponding to all of the primary code digits or all but the last digit of the primary code, whereupon the signal on line 23 will cause that portion of the primary code to be stored. At the same time, actuation of latch 16 diverts the output of the primary code 14 onto line 34 coupling it to the alternate code 26. Now in order to obtain an output 33, either the ignition switch 13 is closed (if the alternate code is unused) or the code selector coupled to the alternate code 26 must be actuated and then the selector representing the final digit of the primary code sequence. In the hold or alternate code mode, the latch mechanism 16 may also be coupled to means for flashing the headlights or means for limiting the time during which the system is operable, or other mechanisms to provide further deterrents to unauthorized usage.

Turning now to FIG. 2, specific circuitry is shown for one means for carrying out the principles of my invention. An ignition switch 50 is typically coupled to the positive terminal 51 of the electrical system, usually 12 volts DC. Terminal 52 of switch 50 is coupled to the starter terminal 52 and terminal 53, which is in the normal automotive ignition coupled directly to the ignition system, is here coupled into the circuit of the present invention. Terminal 54 is likewise coupled to the positive terminal of the DC power source and the circuit shown in FIG. 2 is principally designed for use in a system having a negative ground potential as evidenced by terminal 55 coupled to ground. It is contemplated that the circuit shown herein may be used with the customary key operated ignition switch 50 or the ignition switch may be dispensed with in favor of using in its place the coded switch of the present invention, there remaining the requirement for some type of switch to activate the starter motor. As will be further explained below, this system may also be so connected as to store the primary code thereafter permitting use of just the ignition switch to activate the ignition until the release button is pressed.

Terminal 53 is coupled to a diode 56 of the polarity shown, the cathode of which coupled to junction point 58 at which a positive potential will be imposed when the ignition switch 50 is closed or when the code switch is activated to bypass the primary code. Positive potential from junction point 58 will be conducted through line 60 to junction 62 where it couples to the input of two primary code switches generally designated 64 and 66. The system includes a plurality of momentary contact, push button switches provided in a typical keyboard configuration (not shown) and only those selected push buttons which are to be a part of either the primary or alternate code are coupled into the circuit as are switches 64 and 66. The remaining switches such as 68 representing the remaining digits not selected as part of the code sequence, wherein the switch shown at 68 is designated by the numeral "N" to designate the remaining digits, are all coupled to ground potential at one of the terminals thereof the other terminal being coupled to terminal "B" which is in turn coupled through resistor 70 to ground potential. More will be said subsequently as to the effect upon the circuit when any of the switches exemplified by 68 are actuated.

Resistor 72 is coupled to junction point 62 and to the anode of a silicon controlled rectifier (SCR) 74. The cathode of SCR 74 is coupled to ground at 76 and the gate electrode 77 is coupled to terminal 78 of switch 64 and also through resistor 70 to ground. It will be seen that depressing button 80 of switch 64 will close the circuit between terminals 78 and 79 thereof which are coupled to junction point 81 momentarily placing a positive DC potential at gate electrode 77 of SCR 74 causing current to flow through the SCR to ground. Upon releasing button 80, current will continue to flow through SCR 74.

Switch 66 is coupled in series with switch 64. Here, resistor 82 is coupled to junction point 62 and to the anode of SCR 84, the cathode of which is coupled to junction point 86. The gate electrode 87 is coupled to terminal 88 of switch 66 and through a resistor 90 to junction point 86. Junction point 86 is in turn coupled to terminal 92 of switch 64. Depressing button 94 of switch 66 momentarily closes terminals 88 and 96 placing a positive potential across SCR 84 causing it to conduct, and release of button 94 will permit SCR 84 to continue to conduct, if switch 64 has been first actuated causing SCR 74 to conduct and then released to the position shown in FIG. 2, wherein contacts 92 and 98 are closed. Thus, if button 94 were momentarily depressed before button 80, at which time SCR 74 was nonconducting, SCR 84 would not conduct because there would be no conducting path to ground.

A relay 100 having a coil 101 has one terminal thereof coupled through line 102, line 104, to one of the switch elements 106 of relay 100 which is in turn coupled through line 108 to terminal 53 of the ignition switch. The other terminal of relay coil 101 is coupled through line 110 to the anode of SCR 112, the cathode of which is coupled to junction point 114. The gate electrode 115 of SCR 112 is coupled to terminal 116 of switch 118 and through resistor 120 to junction point 114. Junction 114 is coupled through line 122 to switch element 124 which is a portion of relay contacts associated with relay 127. In its primary code condition, switch element 124 is normally in contact with terminal 126 which is coupled through line 128 to terminal 130 of switch 66. When push button 132 is depressed, closing contacts 116 and 134, sCR 112 will be triggered to conduct if push buttons 80 and 94, have, in sequence, been depressed causing conduction in SCR's 74 and 84 providing a continuous, series path to ground. In this situation, when current is caused to flow through SCR 112, current flows through relay coil 101 actuating switch element 106 thereof moving said switch out of contact with terminal 136 and into contact with terminal 138. When switch part 106 makes contact with terminal 138. When switch part 106 makes contact with terminal 138, it will be seen that a positive potential is applied through line 108 to conductor 140 providing a positive potential at output terminal 142, thereby providing power to the ignition circuit. The remaining terminals of the ignition circuit are coupled to ground potential as indicated at 144.

Relay terminal 136 when in contact with switch part 106 provides DC potential at a second output terminal 146, terminal 148 being at ground potential. This set of outputs 146 and 148 provides a second set of output lines which may be coupled to any appropriate locking, warning, or other mechanisms for use as additional security devices on an automobile or the like. As an example, the output signals on the second set of lines may be used to power appropriate solenoid locks to be applied to the hood or trunk lid of an automobile or a steering wheel or transmission lock to further prevent theft of the vehicle. Many uses of the second set of outputs may be obvious to those persons skilled in the art.

When ignition switch 50 is closed and a positive DC potential appears at junction 58, current will also be conducted through line 150, through contacts 152 of relay 126, line 154 to a time delay mechanism generally designated 156. The time delay mechanism 156 as shown herein includes appropriate biasing resistors 158, 160 and 162 and capacitors 164 and 165 with resistors 166 to provide an RC charging circuit capable of firing the unijunction transitor 168 when the charge on the capacitors reaches a predetermined level. When that occurs, a potential will be applied on the gate electrode 170 of an SCR 172 causing current to flow through resistor 174, through the SCR 172 through relay contacts 176 of relay 100, through resistor 166. If the SCR 172 fires before push buttons 80, 94 and 132 have been depressed in sequence to complete the series circuit through relay coil 101 to ground, to actuate relay 100, then the potential across the coupling capacitor 178 will be discharged through the SCR 172 interrupting any current flow through SCR 74 thereby disabling the system, or in other words interrupting the series circuit through the switches 118, 66 and 64 to ground.

This condition in which the series circuit to ground is interrupted will remain for a fixed period of time as determined by the RC time constant of the time delay circuit 156 following which the SCR 172 stops conducting permitting the operator of the system to again try to actuate the buttons in the proper sequence to complete the circuit before the time delay interrupts the circuit once more. On the other hand, if the sequence is properly completed and relay 100 is actuated, relay 100 will cause a change in the contacts 176 in the time delay circuit interrupting current flow through the SCR 172 thereby removing the time delay circuit from the system.

If any of the other switches 68 which are not part of the series circuit are depressed at any time before or after switches 64, 66 and 118 are actuated, they will interrupt current flow through SCR 74 by coupling terminal point B to ground shutting off SCR 74. Thus, in its primary code sequence, it is necessary to actuate the three buttons of the primary code here representing digits 3, 5 and 9 in that sequence before the time is reached as established by the RC time constant of the time delay circuit 156 so that the series circuit is completed through relay coil 101 which then actuates switch contact 106 into contact with terminal 138 providing power to the ignition circuit. Unless that specific sequence is followed, the time delay takes over and disables the circuit for a predetermined period of time. Additionally, if one actuates any of the other push buttons the system is disabled at any point even after push button 132 has been actuated. Thus, the operator must know the proper code sequence and execute it accordingly within the time provided or the application of the power to the ignition system will be interrupted. In FIG. 2, the push buttons 80, 94 and 132 have been coded with exemplary digits 3, 5 and 9 which would to the operator indicate the numerical code sequence 3-5-9 as being the primary code. The unused switches 68 may be coupled through a two position switch 69, which is either operated independently or as a part of relay 127. Switch 69 is connected to ground, and each of the "N" buttons is coupled to terminal B so that actuation of any of the unused buttons will disable the primary code circuit by shorting the gate of SCR 74 to ground. It will be observed that after buttons "3" and "5" have been actuated, a second actuation of button "3" will disable "5". In the alternate code mode, switch 69 moves to contact 69a, connected to junction 212 thereby grounding the cathode of SCR 206. Thus, the unused "N" buttons and the primary code buttons "3" and "5", are of no further effect in disabling the circuit so a parking attendant cannot destroy the alternate made by incorrect button use. If switch 69 is actuated by relay 127, this function is automatic, but the use of switch 69 may be optional.

In order to permit use of the system by another authorized person, and without disclosing to anyone the primary code sequence 3-5-9, the system permits a change or substitution of the primary code through the use of the same keyboard. A hold button 180, normally open, has one terminal 181 thereof coupled through line 182 to the positive potential terminal 54. The other terminal 183 is coupled to terminal 184 of a release switch 186. The other terminal 188 of switch 186 is coupled through coil 190 of relay 127 to ground. Depression of the hold button 180 causes current to flow through terminals 181 and 183 and through the normally closed release switch 186, through relay coil 190 causing relay 127 to be actuated. When that happens, relay contacts 152, 192 and 124 all change position. When relay contacts 152 change position potential is removed from line 154 which couples to the time delay circuit 156 whereupon the time delay circuit is removed from the system. the relay contacts 192 change, contact is made on line 194 which is coupled to potential terminal 54 whereupon current conducts through line 194 through contacts 192, through line 196, through normally closed switch 186 and then through relay coil 190 so that relay 127 is held in this condition. If desired, an indicator lamp 198 may be included coupled between line 196 and ground so that a visual indication is provided of when the system has been placed in its alternate code condition. Now, DC potential is also applied through line 194, through relay contact 153 and through line 150 to junction 58 which is coupled to line 60 so that potential was once more applied at junction point 62. Now the primary code may be stored in the system by depressing in sequence buttons 80 and 94 causing SCR's 74 and 84 to conduct.

When relay 127 is actuated, switch part 124 moves out of contact with terminal 126 and into contact with terminal 200. This now places an additional SCR switch element in series between switches 66 and 118. This additional switch 202 may be any of the other unused plurality of switches available in the keyboard. The circuit configuration of the elements coupled to switch 202 is similar to that already described, including a series resistor 204, SCR 206 with its gate electrode 207 coupled to terminal 208 of switch 202, and also through resistor 210 to junction point 212. Junction point 212 is coupled through line 214 to terminal 130 of switch 66. Now with portions of the code already stored in the system, the owner of the system need only inform a parking lot attendant or the like that in order to actuate the system he need only press buttons 216 and 132. Button 216 has been assigned digit 8 for the purposes of this explanation. Accordingly, the owner of the system merely informs the attendant that in order to actuate the system he serially depresses numerals 8 and 9 on the keyboard and the system will function properly. Since the time delay has been removed from the circuit, it does not form a part of the system in the alternate code mode.

The system is readily returned to its primary code condition by actuating release switch 186 which interrupts current flow through terminals 184 and 188 thereof, momentarily interrupting current flow through relay coil 190 causing the contacts associated with that relay to return to their original condition. It will be noted that in this embodiment, the alternate code sequence is preestablished. This may be avoided by adding to the circuit a rotary switch or equivalent coupling SCR 206 selectively to all the unused switch buttons so the operator can select any unused digit as the first element of the alternate code sequence.

Turning now to FIG. 3, there is shown an alternate embodiment of the circuit containing many similar features but providing the additional flexibility of permitting temporary selection of the alternate code sequence. In other words, the circuit shown in FIG. 2 provides a fixed alternate code in terms of the previously selected digit 8 of switch 202 whereas in the circuit shown in FIG. 3, any one of the unused digits may be inserted as an element of the alternate program code. In FIG. 3, similar features of the circuit as compared to FIG. 2 are shown by the same reference numerals and the ensuing description will deal only with the alternations therein.

As before, closure of ignition switch 50 provides positive DC potential at terminal 53 and on line 250. Current is conducted through normally closed contact 252 and switch part 253 of relay K2 to junction point 62. Depression of switch button 80 causes SCR 74 to conduct and upon release of that switch part, SCR 74 will continue conducting. Also, actuation of push button 94 will cause SCR 84 to conduct after SCR 74 is conducting and release of button 94 will permit SCR 84 to continue conduction. Then when push button 132 is actuated closing contacts 116 and 134, SCR 112 will conduct causing current flow through coil 100 of relay K1. Current will flow to junction point 114, through switch part 254 of relay K4 which is normally in contact with terminal 255 permitting current to flow to junction point 212 which is in series with terminal 130 of switch 66. Thus, the series circuit is completed and current flowing through relay coil 100 will cause relay contacts 106 and 136 to open closing relay contacts 106 and 138 permitting current to flow through line 140 to the output terminal 142. Before the proper contact buttons are depressed, that is buttons 80, 94 and 132, if current is permitted to flow through contacts 106, 136 and then through line 256 which is coupled through a thermal time delay relay 258, excessive current flowing therethrough will cause contacts 260 to open, so that even though the proper switch contacts are thereafter actuated, current may be interrupted to the output 142. Current flows through the time delay relay circuit 258, through terminal 262, switch part 264, which is coupled to line 266 which is coupled to a common line 268 to which are coupled one of the normally open terminals of each of the unused switches 270 to 276. The other normally open terminals of each of the switches 270 to 276 are coupled through line 278 to switch element 280 of relay K4 which is coupled in turn to terminal 282, connected to ground. Thus, if the operator should depress any of the unused switches 270 to 276, current will flow through the time delay relay 258 because it is thereupon coupled to ground through terminals 106 and 136 causing the resistance element in the time delay relay 258 to open the contacts 260.

In order to switch to the alternate code sequence, the hold switch 180 is first depressed causing current to flow through contacts 181 and 183, conducting current through the normally closed release switch 186 and terminals 184 and 188 thereof to supply potential to the coils 284 and 286 of relays K4 and K2. When current flows through relay coil 284, contacts 280 and 282 are opened thus removing the ground connection of the time delay relay 258 so that it is thereby removed from the circuit. In addition, relay K4 causes a change in position of the relay contacts 254 and 255, causing switch element 254 to close contact with terminal 288. At the same time, relay K2 causes a change in position moving contact element 253 in contact with terminal 290 providing DC potential to junction 62 and closing contact between elements 292 and 294. When elements 292 and 294 come in contact, current is supplied on line 296 to the release switch 186 and also on line 298 supplying current to common bus 300 for purposes which will become apparent hereafter. Relay K4 also changes contacts 262 and 264, moving switch element 264 into contact with terminal 302 thus supplying positive DC potential from junction 62 through line 304, through contacts 302 and 264, through line 266 to line 268.

With all the relay contacts changed as previously described, the operator now enters the first two digits of the primary code, closing switches 64 and 66, causing their respective SCRs to conduct. Now to program the alternate code, the operator selects any of the switches 270 to 276. If he actuates switch 270, for example, coded for the digit "8", current will flow through contacts 306 and 308 onto line 278, and then through all of the normally closed remaining switches 271 to 276. For example, current flows through normally closed switch 271 to line 310 and thence through relay 312 closing contacts 314 and opening contacts 316. Similarly, all of the relays corresponding to all the other switches which were not actuated will likewise close. No current will flow through the relay 316 corresponding to switch 270 so contacts 320 and 322 remain as they were. The relays coupled to switches 270-276 have double coils such as 312a and 312b of switch 271. When contacts 314 are closed by current through coil 312a, voltage supplied on bus line 300 conducts current through coil 312b to hold the relay closed. The same condition occurs for switches 272-276. Now in order to energize the locking circuit, the attendant is told to actuate the switch coded "8" and "9". When switch button 270 is first actuated, with the ignition 50 on, current flows through conductors 278, 332 and 333, contact 334 to coil 324 of relay K3 which would cause a change of position in the contacts, closing 326 and 328 and SCR 206 would be triggered to conduct through line 330. After switch 270 is released, current would stop in coil 324 and contacts 326 would again make contact with 335 coupling SCR in series with SCR's 66 and through now closed contacts 288 and 254 of relay K4 to SCR 112.

Then when switch 132 is depressed, SCR 112 will conduct and all of the SCRs 112, 206, 84 and 74 are in series completing the code sequence so that current through coil 100 again occurs causing relay K1 to supply power to the output terminal 142.

The system may be readily returned to its primary code sequence by actuating the release switch 186 which interrupts current flow to the relays K2 and K4 returning all of the aforementioned contacts to their normal positions, that is the condition shown in FIG. 3. Similar to FIG. 2, relay K1 can also be provided with a second set of output terminals for connection with other external locking mechanisms.

It will thus be readily apparent that the two embodiments of the circuitry shown herein provide an extremely simple and economical method for providing a substitute for the traditionally used key operated ignition switch which may hereafter be done away with in favor of an ordinary switch which is not key operated, since there no longer remains a necessity for the use of a key, that function being supplied by the encoded locking system of my present invention. Whether or not the first or second embodiment of my device is used, a means is provided through the use of the same keyboard operation to change the combination so that there is no necessity for disclosing the secret code sequence to anyone except the owner thereof. This secret code sequence can be bypassed and an alternate code sequence used to permit easy access to the use of the vehicle by authorized persons who can then be informed of the alternate code sequence. The theft preventative measures such as the time delay circuits described herein and the use of secondary outputs to provide locking mechanisms or alarm devices are all bypassed when the system is in its alternate code sequence so as to provide no inconvenience to parking lot attendants and the like. Similarly, it will be noted that in the alternate code condition of the circuits shown in the drawings, there is no alarm or time delay so the attendant may take as long as necessary to apply the proper code sequence without disabling the system. However, it may be desirable to discourage theft when the device is in the alternate code as well. This is readily accomplished by inserting a counter in line 266 (FIG. 3) and keeping the time delay activated after depressing the hold button. The counter is coupled to the time delay and disables it unless it receives a preselected number of wrong code sequence signals. Thus, a parking attendant can make a limited number of attempts to use the proper code sequence, usually enough attempts to get it right, but someone else would not have free time to try to guess the alternate code, which may only consist of two digits.

As a further modification of my invention, the alternate code sequence may be eliminated if it is desired to use the locking mechanism in conjunction with key operated ignition systems. In such a case, the code latch 16 of FIG. 1, that is the hold and release switches 180 and 186 of FIG. 2, and their functions would be retained so that the vehicle owner can insert the primary code as previously described. Diode 56 would be removed and line 104 connected directly to junction 62 instead of to 106. When hold button 180 is momentarily depressed, the vehicle owner enters the primary code as previously described, closing relay contacts 106 and 138. Thereafter the ignition switch 50 may be used repeatedly to start and stop the motor until the release button is depressed, returning the system to coded operation. It is also contemplated that in line 266, FIG. 3, a counter may be added in series to further disable the time delay relay to permit a fixed number of srong code sequences to be utilized without actuating the time delay for the purpose of further providing some degree of convenience to the operator.

Accordingly, while several embodiments of the present invention have been shown and described herein, changes and alterations will occur to those skilled in the art and it is the aim hereof to include herein all such changes, modifications and their equivalents as fall within the true scope and spirit of this invention.

Claims

What is claimed as new and desired to be secured by Letters Patent of the

1. A combination-coded electrical locking system which enables an external circuit when at least one of a series of digits selected from two or more sequences of digits are entered into the system, comprising:

code selector means having a plurality of input means, each of said input means having a characteristic digit assigned thereto;

a primary code circuit coupled to said code selector means whereby preselected ones of said input means establish a first sequence of primary code digits, said prim ry code circuit including output means responsive to said preselected input means to provide an output signal only when the digits of said primary code are entered according to said first sequence;

an alternate code circuit coupled to said code selector means, said alternate circuit including means coupled to additional ones of said input means to establish a second sequence of alternate code digits, said alternate code circuit including output means responsive to said additional input means to provide an output signal only when the digits of said alternate code are entered according to said sequence;

code latching means coupled to said primary and said alternate code circuits, said code latching means including means for selectively disabling said primary code circuit and simultaneously enabling said alternate code circuit; and

external circuit enabling means coupled to the outputs of said primary and said alternate code circuit means, said external circuit enabling means having means responsive to an output of either of said code circuit means

2. The system set forth in claim 1 wherein said alternate code circuit is coupled to preselected ones of said input means thereby establishing a

3. The system set forth in claim 1 wherein said alternate code circuit is coupled to a plurality of said input means one of which is also coupled to said primary code circuit such that said primary and alternate code

4. The system set forth in claim 1 wherein said primary code circuit and said alternate code circuit are each coupled to two or more of said input

5. The system set forth in claim 1 wherein said alternate code circuit includes selector circuit means coupled to said input means for selecting the digits comprising said alternate code sequence, said selector circuit means being enabled by said latching means whereby said selector circuit means becomes responsive to the actuation of selected ones of said input means to couple the same into said alternate code circuit according to a

6. The system set forth in claim 3 wherein said primary code circuit and said alternate code circuit are each coupled to two or more of said input

7. The system set forth in claim 1 further including disabling means coupled to said primary code circuit, said disabling means responsive to the input means coupled to said primary circuit to disable said circuit whenever an input is actuated having a characteristic digit not an element of said primary code sequence or not in the correct sequence, time delay means coupled to said disabling means to establish a time interval during which said disabling means is maintained in an inoperative state, and said latching means coupled to said time delay means to render the same inoperative when said latching means is in the state disabling said

8. The system set forth in claim 1 further including disabling means coupled to said primary code circuit, said disabling means responsive to the input means coupled to said primary circuit to disable said circuit whenever an input is actuated having a characteristic digit not an element of said primary code sequence or not in the correct sequence, time delay means coupled to said disabling means for establishing a time interval during which said primary circuit is held in the disabled state in response to an improper digit entry, said latching means being coupled to said time delay means to disable said delay means when said latching means

9. The system set forth in claim 1 wherein said primary code circuit comprises:

a plurality of silicon controlled rectifiers coupled in series circuit relationship, means coupling said selected input means of said primary code to each rectifier to sequentially initiate conduction therein according to said primary code sequence, the last one of said selected

10. The system set forth in claim 9 wherein said latching means comprises:

means for supplying electrical potential to said selected input means of said primary code circuit, said alternate code circuit comprising switching means coupled between the output of said primary code circuit said source of electrical potential and said external circuit enabling means whereby electrical power is supplied to said enabling circuit through said alternate circuit means when said primary circuit means is

11. The system set forth in claim 9 wherein said latching means comprises:

means for supplying electrical potential to said selective input means of said primary code circuit, said alternate code circuit including switching means coupled intermediate two of said series connected silicon controlled rectifiers of said primary code circuit, input means coupled to said

12. The system set forth in claim 11 wherein said alternate code circuit comprises:

second circuit means comprising one or more silicon controlled rectifiers each coupled to ones of said input means other than those of said primary code circuit, said input means coupled to said rectifiers to initiate

13. The system set forth in claim 11 further including time delay means coupled to said primary code circuit, said time dealy means operative to disable said primary code circuit for a preselected period of time, and wherein said latching means further includes means coupled to said time delay means for disabling said delay means when said latching means

14. The system set forth in claim 9 wherein said primary circuit means comprises silicon controlled rectifiers coupled in series and with each of said selected input means, each of said input means comprising switch means having a normally closed first position and a momentary closed second position;

the first controlled rectifier coupled to the switch means corresponding to the first digit of said primary code sequence having the cathode thereof connected to ground, the anode thereof coupled to said switch means in the first position thereof and to a source of electrical potential, the gate electrode of said controlled rectifier coupled to said source of electrical potential through said switch means when the same is in said second position, whereby movement of said switch to said second position initiates conduction in said controlled rectifier which conduction continues after said switch is returned to said first position;

the second controlled rectifier coupled to second switch means corresponding to the second element of said primary code sequence, said second controlled rectifier having the cathode thereof coupled to the anode of said first controlled rectifier when said first switch means is in said first position, the anode of said second controlled rectifier coupled to said source of electrical potential through said second switch means when in the second position thereof, whereby movement of said second switch to said second position after movement of said first switch to the second position thereof initiates conduction of current through said second controlled rectifier and said first rectifier to ground which conduction continues after said second switch is returned to said first position.