EP0292217A2

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Info

Publication number: EP0292217A2
Application number: EP88304408A
Authority: EP
Inventors: George Lambropoulos; Robert A. Hair; Kenneth R. Pitera
Original assignee: Wickes Manufacturing Co; TRW Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1987-05-21
Filing date: 1988-05-16
Publication date: 1988-11-23
Anticipated expiration: 2008-05-16
Also published as: JPH0791913B2; JPH09324567A; DE3856232D1; JP3413338B2; EP0831197A2; EP0292217A3; EP0292217B1; DE3856578T2; DE3856232T2; JPS63308171A; DE3856578D1; EP0831197A3; EP0831197B1

Abstract

A remote control system which includes (a) a receiver unit adapted to be fixedly mounted on a motor vehicle having at least one door lock with a first locked condition and a second unlocked condition and having means for receiving a coded signal including a code portion of binary bits, memory means for storing a first code of binary bits, means for comparing the code portion of a received coded signal with the first code and means for shifting the controlled device to one of the conditions upon the comparison match between the code portion of a received signal and the stored first code and (b) a transmitting unit for transmitting the stored second code of binary bits when the door lock is to be shifted into one of its conditions. In this system the invention involves the improvement wherein the coding of the second code set into the transmitter is a unique group of binary bits and the receiver unit includes a field programming arrangement for setting the first code of the receiver unit to the unique group of binary bits in the transmitting unit by using the signal from the transmitting unit as received by the receiver unit. In accordance with this improvement, the first code of the receiver unit is set to the second code of the transmitting unit in the field and may be changed from one code to another code upon authorized use of a second transmitting unit having its own unique code.

Description

The present invention relates to the art of controlling the door locks of a motor vehicle and more particularly to an improved remote control system for unlocking and locking vehicle doors utilizing a hand held transmitting unit or transmitter.
The invention is particularly applicable for use in remote control of the door locks in a motor vehicle and it will be described with particular reference thereto; however, the invention is equally applicable for actuating various control devices on a motor vehicle, as well as control devices on other structures such as locks on residential doors and mechanical garage door operators.

INCORPORATION BY REFERENCE

Perron 4,031,434 is a prior art patent illustrating an inductively coupled vehicle door lock system wherein a binary coded signal is transmitted from a hand-held transmitter to a vehicle mounted receiver which recognizes the binary code and compares the code to a programmable lock code for the purpose of selectively locking and unlocking a vehicle door. This general control system is incorporated as background information. This patented unit is not a remote control unit in that the key member must be positioned adjacent the receiver for the purposes of actuating the door locking motors. Actual remote control systems are disclosed in Bongard 4,596,985 and Barreto-Mercado 4,607,312. These two patents are also incorporated by reference herein as being representative of prior art control systems employing one or more binary codes for the purposes of actuating devices from a remote position by transmitting a binary code to a receiver for recognition and processing. A specific code can be set into the transmitters of these two patents by dip switch coding, by punched hole coding, such as cutting resistors, and by using a plug-in code unit.

BACKGROUND OF THE INVENTION

For many years the automotive industry has sought a remote control system which could be assembled into a motor vehicle at the factory and employed by the ultimate purchaser for controlling various functions of the motor vehicle from a hand-held transmitter. Such systems were envisioned for operating the door locks and trunk latch so that the driver could lock the doors upon leaving the vehicle or unlock the doors as approaching the vehicle. In addition, it was anticipated that such remote control system should also operate the trunk latch so that a hand-held transmitter could be employed for the purpose of unlocking the trunk as the driver approached the vehicle for the purpose of facilitating loading of the trunk without the need for manipulating a key which can present difficulties and inconveniences when burdened with packages, at night when vision is hampered or when ice inhibits insertion of a standard key. Such remote control systems have been sought by the automobile industry for the purpose of either standard equipment or as an option; however, even though the concept appears quite susceptible to implementation, substantial problems have been enountered in efforts to develop such a successful remote control system. These difficulties have caused much interest in an approach which satisfies the demands of the automobile industry regarding price and lack of customer complaints.

The most prevalent concept to be employed for such a remote control system has been the use of a binary identification code which is transmitted from a transmitter by employing a modulated radio frequency signal having a coded portion that is indicative of an identification binary code. The binary code of such suggested system is fixed into the receiver and is outputted as a series of pulses of the radio frequency, which pulses have intelligence constituting the desired identificaton code. This binary identificaton code is fixedly contained in a receiving unit secured onto the motor vehicle, which receiving unit has a detector that allows passage of the particular radio frequency of the transmitter. Filters or other processing circuits convert the incoming coded signal into a replica of the binary code from the transmitter. This replica is compared to the identification code in the receiver and determines whether or not the coded portion of the transmitted signal matches the identification code stored in the receiver. Upon acknowledgement of a match between an incoming code portion of a received signal and the stored identification code in the receiver, the door lock is actuated. In accordance with this remote control concept, the identification code being transmitted to the receiver is accompanied by an appropriate function code of a binary nature which function code is decoded upon matching of the identification code so that the desired function will be initiated by the receiver mounted in the motor vehicle. This desired function can be to lock the door, unlock the door or unlatch the trunk. Of course, other desired functions could be incorporated into the transmitted signal and identified by the receiver, such as activating the ignition system, initiating a security system, flashing the headlights, activating the horn, etc. to mention only some of the more obvious functions which could be controlled by the receiver upon identification of the proper incoming signal. Technology for accomplishing these various control functions is available. Many variations of this control theme have been suggested for controlling the door locks or the trunk latch of a motor vehicle.

Extensive effort to incorporate a remote control system, as explained above, as an OEM installation for motor vehicles has resulted in serious technical and practical impediments. Since the identification code in the receiver and transmitter must be functionally identical, the receiver and transmitter must be kept together during the assembly of the vehicle. Since it is necessary that the receiver be mounted in an unaccessible, hidden position in the vehicle, the transmitter matched to the receiver must remain with the car as it is being assembled, painted, transported, displayed and sold. Should the transmitter be separated from the motor vehicle, the system is useless without some code arrangement maintained associated with the vehicle. A replacement transmitter would not have the same identification code as the factory mounted receiver. Consequently, the receiver would have to be disassembled, recoded, and matched with a new transmitter. The capability of accomplishing this goal is self-defeating, since the receiver now must be easily accessible and easily reprogrammed for a new identification code. The advantage of original equipment on the vehicle employing a remote control system is that the receiver can be assembled in the motor vehicle at a remote or hidden location so that disassembly and recoding is impossible. Only in this manner can the ultimate purchaser of the vehicle be assured that other persons do not gain access to the vehicle with another remote control transmitting unit. In addition, when a receiver is mounted at the factory, problems can be experienced when the hand-held transmitter unit is lost or misplaced. A new hand-held transmitter will not have the code of the receiver on the vehicle. One arrangement for solving this particular problem would be for the code of the receiver to be in some manner, maintained by the dealer or by the purchaser. Then, a manually manipulated coding arrangement could be imparted to a new transmitter for code matching purposes. To use this concept, the programming must be somewhat rudimentary and simple which defeats the intended security level of the system and destroys the basic objective of the original implementation of a factory assembled remote door lock control system. With the code being maintained by the dealer, security is compromised and record keeping must extend for the life of the vehicle. These factors are unacceptable.

Other difficulties have been experienced in matching receivers and transmitters employing binary transmitted codes. If a second transmitter is desired for use by another person, it must match to the transmitter originally supplied with the vehicle. To do this, the transmitter code must be read externally or again maintained by the dealer. A person finding the transmitter unit or gaining access to the dealer records could determine the code and prepare a duplicate without the car owner knowing that a duplicate transmitter exists.

As can be seen, the concept of mounting a receiving unit in the vehicle itself in an inaccessible location at the factory and also producing a security code concept which cannot be manually duplicated by anyone having the original transmitter, another tramsmitter or access to dealer records presents serious problems. These problems have resulted in the inability of the automobile industry to develop a remote control system which is acceptable to the public and unobtrusive to the vehicle manufacturer with respect to code correlation and identification code security.

THE PRESENT INVENTION

The present invention relates to a remote control system to be used for operating the door lock of a motor vehicle and which overcomes all the disadvantages of systems heretofore developed of the type having a receiver mounted at the factory in an inaccessible location on the vehicle. This system includes a transmitter that need not be matched with the assembled receiver, until delivery of the motor vehicle to the ultimate purchaser.

In accordance with the present invention, there is provided a remote control system of the type including a receiving unit adapted to be fixedly mounted on a motor vehicle and having at least one door lock with a first locked condition and a second unlocked condition. The receiving unit includes means for receiving a coded signal, including a code portion of binary bits, memory means for storing a first code of binary bits, means for comparing the code portion of a received coded signal with the first code and means for shifting the door lock to one of the conditions upon a comparison match between the code portion of a received signal and the stored first code. A corresponding transmitting unit is employed which includes means for storing a second code of binary bits, selector means for indicating a desire to shift the door lock to one of the conditions, means responsive to the selector means for transmitting a coded signal including a second code at the code portion of the transmitted signal. This transmitted signal has a signal strength sufficient to drive the receiving means when the transmitting unit is in proximity to the receiver unit. This system further includes programming means for setting the first code to match the second code by coding the second code to a unique group of binary bits and then field programming the first code into the receiver with the unique group of binary bits by using the signal transmitted from the transmitting unit for such field programming.

By using the present invention, a unique binary code is loaded into a transmitting unit. This unique code is randomly selected from a source, such as a number generator, when the transmitting unit is first manufactured and shipped. Consequently, the transmitting unit has a specific unique binary code, which code is not correlated during the manufacturing thereof in any fashion with a particular receiver unit. In the field, after the vehicle has been fully assembled with a transmitter unit located in a secure location within the vehicle itself, the transmitting unit itself is used for programming the code in the receiver. By employing this aspect of the invention, there is no need to match a receiver unit and transmitting unit. A universal receiver unit is assembled into all the motor vehicles and then programmed to match a particular hand-held transmitter.

In accordance with another aspect of the present invention, the receiver unit includes a universal code when delivered to the automobile factory, so that all receivers have the same universal code when they are assembled at the factory. In this fashion, a special transmitting unit at the assembly plant is set to the universal code and can test the operability of each receiver unit without regard to the identification code which will be subsequently set into the receiver unit.

The manufacturer of the transmitting units and receiving units can provide a different universal code for different automobile manufacturers so that receiving units for each automobile manufacturer can have a different, known universal code. The universal code is for manufacturing convenience and not for ultimate security. The dealer, upon receiving delivery of the vehicle, will receive a transmitting unit having a unique code or have a supply of these units each having its own code. Upon delivery to the ultimate purchaser, the dealer will use a transmitting unit randomly selected by the manufacturer or dealer, but having a unique code, to shift the universal binary code loaded into the receiver at the factory to the unique code of the randomly selected transmitter provided to the purchaser by the dealer. By utilizing this unique coding scheme, there is no need to match receivers and transmitters. A replacement transmitter can be supplied at anytime and used in the system by merely changing a receiver unit identification or security code to match the unique binary code of the replacement transmitter.

In accordance with another aspect of the present invention, the receiver unit of the system includes more than one register for storing a group of binary bits. Each group of bits constitutes a first code of the receiver means. A write enabling means is provided, so that a manually operated switch, at the receiver, can enable all registers to accept the binary code received by the receiver unit from any randomly selected transmitting unit. By providing a write enabling signal manually and transmitting a coded signal from a randomly selected transmitting unit to the enabled receiving unit, the codes in the registers of the receiving unit are shifted from either the universal code (during initial programming) or an existing code, to the binary code of the signal being received from the transmitting unit. By this aspect of the invention, the code of the receivers can be set in the field by use of any transmitting unit. Thereafter that transmitting unit becomes the matching unit for remote control of the receiver.

In accordance with another aspect of the invention, after a first identification code is loaded into all registers of the receiver, a second code can be loaded into the registers from a second randomly selected transmitting unit. This second code will load each register of the receiver, except for a first register. Consequently, the first register retains the first code setting. During a preselected time, such as 30 seconds, a third code can be loaded from a third transmitter. This code by-passes the first and second register and loads all subsequent registers, if any are in the receiver. In this fashion, two or more transmitting units can be employed for setting an identification code in a receiver. Consequently one of the two or more transmitting units employed for setting the codes during the preselected time can be recognized by the receiver unit for operating the door locks and other controlled device.

When a WRITE signal is created, all registers in the receiving unit remain enabled for the preselected time. During this preselected time, the first code received by the receiver loads all registers; therefore any preexisting identification code in any register is removed. By employing this inventive concept, the owner of a vehicle has a particular transmitting unit or units. If the unit or units do not function at all, meaning a new code has been loaded into the registers, the authorized operator will realize that his vehicle has been recorded. Since any recoding destroys all existing coding, an authorized person cannot surreptitiously code a selected unused register of the receiver. By employing this aspect of the invention, an unauthorized person having a transmitting unit and knowing the resetting concept for the receiver unit could not reset the receiver unit to a separate transmitting means without ultimately being realized by the vehicle owner.

During the time when the WRITE signal is initiated for field programming of the receiver, the first code can be received and written into all registers. During a second time, still during the preselect programming time, the second code can be received and written into all registers, except the first. After the WRITE signal has been created, in practice, approximately 30 seconds, the programming process must be repeated. This feature will not allow an authorized person to insert an unwanted identification code at the lower portion of the register stack.

By incorporating these various aspects of the present invention, a secure, remote control system is provided which is field programmable, but which cannot be preempted for unauthorized use of other transmitting units. In accordance with the present invention, the transmitting units each have a unique code which is different from all other codes. In practice, twenty-four bits are employed in the security code; therefore, the unique code in each of the transmitting units need not be duplicated. The use of this concept of a unique randomly selected, not recorded, code for the transmitter and the field programming to this code by the receiver gives extreme versatility and simplicity to the new remote control system. These features made the new system acceptable to the automobile industry for the purpose of OEM installation.

In accordance with another aspect of the present invention, a remote control system, as described above, is provided with a unique arrangement for correlating the recognition factor of the receiver unit with the received signal, whereby the clocking oscillator in the transmitter does not have to be matched with the receiving or clocking oscillator of the receiver unit. By incorporating this aspect of the present invention, matched, crystal controlled oscillators are not necessary for a set of transmitting and receiver units. Without employing a crystal control oscillator in the transmitting unit and without matching the oscillator of the transmitting unit with the oscillator of the receiver unit, the system, when using this aspect of the invention, recognizes the proper code and is positive in operation. The receiver is synchronized with the transmitter by using the incoming signal of the receiver. Noises and changes in magnitude of the signal caused by the different locations of the transmitting unit with respect to the receiving unit during successive operations of the system are not major factors in operation of the system itself. In accordance with this aspect of the invention, the transmitted binary logic signal includes a succession of windows (each a bit) wherein a given logic state is held for a first time indicative of the first binary number or for a second different time indicative of the second binary number. Transmitted coded signals involve a series of pulses each having a pre-selected time correlating with the time of a signal window. Such windows extend between two successive leading edges of the transmitted coded signal. By employing this coding concept, the logic state can be transmitted as a percentage of the signal window or bit in the coded signal, i.e. 80% of a bit is a

logic

1 and 20% of a bit is alogic 0. At the receiver a leading edge detector can record the time between successive leading edges of the coded signal, which time can be averaged to produce a corresponding window, or bit length, in the received coded signal. By correlating the window, or bit length, of the coded signal, the percentage of given logic state indicative of the two binary numbers will allow the binary numbers to be read at the receiver, irrespective of the variations in length of the transmitted window caused by the unregulated oscillator in the transmitting units or other changes in the clocking oscillator of the transmitting unit, or various random noise. The number of windows employed for averaging the length of a window can be changed. It is within the scope of this aspect of the invention to disregard windows or bit length readings having a drastically different length than an expected window length. Such abnormal readings could be indicative of signal spikes or other random noise.

By utilizing this unique coding concept and incorporating this concept with the above-mentioned other aspects of the present invention, an inexpensive remote control system is obtained which can be employed on motor vehicles without limitations heretofore experienced at low cost necessary for use in mass produced motor vehicles.

The primary object of the present invention is the provision of a remote control system, as defined above, which remote control system is inexpensive, need not have matched transmitting and receiving units and which may be programmed in the field in a manner offering security as well as flexibility.

Yet another object of the present invention is the provision of a remote control system, as defined above, which remote control system is easy to program, universal in application and usable in various structural environments including, but not limited to, motor vehicles.

Still a further object of the present invention is the provision of a remote control system, as defined above, which system incorporates a unique coding concept and an arrangement for modifying the receiving unit to accommodate variations in the receiving signal so that imprecise oscillators can be employed without sacrificing the positive operating characteristics of the total system.

Yet another object of the present invention is the provision of a remote control system, as defined above, which system employs a receiving unit which can be mounted in an obscure or hidden location in a motor vehicle, as the vehicle is being assembled, without sacrificing versatility in coding and without requiring matching of the transmitting unit with the receiver unit until ultimate disposition of the manufactured motor vehicle.

Another object of the present invention is the provision of a remote control system, as defined above, which system employs a transmitted binary coded signal utilizing a duty cycle for identifying binary numbers and employing a universal code for operating the system until field programming is accomplished, so that the system may be tested during assembly of the vehicle without final programming of the total system.

Another object of the present invention is the provision of a remote control system, as defined above, which remote control system incorporates a receiver unit which can be reprogrammed in the field and which indicates to the owner of the structure on which the system is mounted that an unauthorized reprogramming has occurred.

Still a further object of the present invention is the provision of a remote control system, as defined above, which remote control system utilizes a transmitting unit having a unique identification or security code which cannot be determined from the transmitting unit itself. In accordance with this object of the invention, the system employs an identification code in the transmitting unit which cannot be set after it leaves the plant or factory in which the transmitting unit is manufactured. Each transmitting unit has its own unique code. This unique code is employed for setting the identification code in the receiver unit so that there is no need for matching transmitting unit and receiving unit.

These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings which are described in the following section.

BRIEF DESCRIPTION OF DRAWINGS

The drawings in the present invention are as follows:

FIGURE 1 is a block diagram illustrating, schematically, the transmitting unit and receiver unit of the preferred embodiment of the present invention employed for controlling door locks and the trunk solenoid of a motor vehicle;
FIGURE 1A is a pictorial view of the transmitting unit in the form of a key holder;
FIGURE 1B is a block diagram illustrating the system employed for outputting coded information from the transmitting unit to the receiver unit in FIGURE 1;
FIGURE 2 is an architecture layout of features contained in the custom integrated circuit employed in the receiver unit of the preferred embodiment of the present invention illustrating certain concepts of the EEPROM used in the receiver unit;
FIGURE 3 is a block diagram and flow chart of the system employed by the receiver unit for programming the receiver unit and for operating various control devices in response to an identified incoming coded signal;
FIGURE 3A is a block flow chart illustrating the system concepts utilizing more than one identification code in the receiver unit shown in FIGURE 1;
FIGURE 3B is a logic diagram illustrating the arrangement for creating a WRITE signal for use in loading the registers of the integrated circuit shown in FIGURE 2;
FIGURE 3C is a logic diagram similar to the logic diagram of FIGURE 3B illustrating the concept for loading successive different codes in the integrated circuit, as shown in FIGURE 2;
FIGURE 4 is a block diagram of the output protion of features performed by the microprocessor employed in the receiver unit of the preferred embodiment as shown in FIGURE 1;
FIGURE 5 is a flow diagram, divided into views 5A, 5B and 5C, illustrating the preferred embodiment of the present invention as it is used in the manufacturing plant and ultimately field programmed;
FIGURE 6 is a logic diagram illustrating the arrangements employed for creating a load releasing signal in the preferred embodiment of the invention;
FIGURE 7 is a block diagram similar to FIGURE 1 illustrating the unmatched, unregulated oscillator arrangement employed in the preferred embodiment of the present invention;
FIGURE 8 is a pulse diagram showing the minimum initiation signal transmitted from the transmitting unit to the receiving unit for initiating the receiving unit;
FIGURE 9 is a pulse diagram illustrating the duty cycle type of pulses during window or bit W for indicating the binary logic in the code portion of the transmitted and received coded signal;
FIGURE 10 is a pulse diagram illustrating the sampling pulses or signals employed in the receiver unit, in accordance with one aspect of the present invention;
FIGURE 11 is a diagram of the logic circuit employed in detecting the binary state of the coded signal during each window or bit of the incoming received coded signal;
FIGURE 12 is a pulse diagram similar to FIGURE 10 illustrating a succession of windows or bits W₄; and
FIGURE 13 is a logic diagram of the system for calibrating the receiving unit to correlate the receiving unit with the actual width of the windows or bits in the coded portion of the received signal.

PREFERRED EMBODIMENT

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting same, FIGURE 1 shows a remote control A for selectively operating a door lock mechanism B, door unlock mechanism C or trunk solenoid D to release the trunk of a motor vehicle. System A includes a transmitting unit T for creating a coded signal S to be transmitted to receiver unit R, whereby the doors of the vehicle can be locked or unlocked or the trunk can be released at will from a distance of at least 20-50 feet. The radiating strength of signal S must be sufficiently weak so that remote control system A is effective when transmitter T is in the general vicinity of the vehicle onto which the receiver unit R is fixedly mounted. Stronger signals S may cause atmospheric electromagnetic interference which could be objectionable under Federal regulations. Transmitting unit or transmitter T includes a special purpose, or custom, microprocessor having appropriate internal PROMs and RAMS programmed to perform the functions of the system, as hereinafter described, and having sufficient I/O terminals controlled by selector means or switches 12, 14, and 16. In accordance with the illustrated embodiment, switch 12 is depressed when system A is to lock the doors of the vehicle by operating mechanism B. In a like manner, switch 14 is manually operated to unlock the vehicle doors by actuating door unlocking mechanism C. The trunk solenoid D or mechanism for unlatching the vehicle trunk is actuated by depressingmanual switch 16. Upon depressing one of these switches 12-16, a power upcircuit 20 directs power to the microprocessor orchip 10 and actuates

oscillators

30 and 32. In the preferred embodiment switches 12 and 16 power system A and cause a single transmission of a coded signal. Thereafter,circuit 20 is deactivated to await a new requested function. Whenswitch 14 is depressed, a single data transmission is initiated. This unlocks only the driver's door of the vehicle.Microprocessor 10 continues to interrogateswitch 14 for a short time, such as 2.5 seconds. If the switch is released during this time,circuit 20 is deactivated. Ifswitch 14 is held for the 2.5 seconds, transmitter T will transmit a second signal having a function portion to unlock all doors of the vehicle. Other arrangements are possible to control the door locks, etc.

Oscillator 30 has a nominal frequency of 310 MHz, in the preferred embodiment, which frequency is essentially the same frequency employed for common garage door operators.Clock oscillator 32 is unregulated in that it does not have a crystal control and may vary as to its frequency with temperature changes and manufacturing tolerances. The output ofoscillator 32 is used to time the function ofmicroprocessor 10 to shiftline 38 to alogic 1 whenever a binary 1 is to be transmitted byantenna 36.Microprocessor output line 38 is one input of ANDgate 39 having a second input controlled by theoutput 31 ofoscillator 30. Conseqently, the signal inoutput 37 ofgate 39 is a series of binary conditions (logic 0 and logic 1) superimposed on a 310 MHz carrier. Consequently, transmitted signal S, whenmicroprocessor 10 is powered bycircuit 20, will be a series of pulses having a length or duration controlled by the logic inline 38. Lines P are now power lines actuated upon command ofcircuit 20.

As will be described later, the code on signal S is binary, with a binary 1 and a binary 0 being distinguished from each other by having a difference in length or duration. This pulse length is controlled by the frequency ofoscillator 32 which is not a high priced oscillator with quartz control; therefore, the relationship between a binary 0 and a binary 1 for the identification code in transmitted signal S is the relative pulse lengths of alogic 1 and alogic 0. These lengths vary according to the particular frequency ofoscillator 32 but maintain their numerical relationship since they are based upon counts of the clock inline 34. In this manner,oscillator 32 can be relatively inexpensive so the frequency or clock inline 34 will not be identical from one transmitter T to another transmitter. Indeed, during different operating conditions in a particular transmitting unit the clock inline 34 can drift in frequency.

By employing the power up concept, power at lines P is not applied to the oscillators and the microprocessor until there is a selection by depressing one of the switches 12-16. When this occurs, power upcircuit 20, which includes the battery (normal 5.0 volts), directs power to the microprocessor for a preselected time which is controlled by a one shot actuated upon applying alogic 0 toline 18. The length of the time of the one shot is sufficient to transmit one control signal. This signal includes, in practice, at least two initiation bits, twenty-four bits of identification code and at least three bits of the function data to indicate which switch 12-16 has been closed. When a switch is depressed, a single data signal is sent; however, after a preselected time another signal, to unlock all doors, is sent ifswitch 14 has not been released. The concept employs standard logic commands to unlock all doors by holdingswitch 14 for a given time. Of course, other functions could be controlled by the remote control system A by incorporating additional selector means or switches 12-16. As illustrated in FIGURE 1A, transmitting unit T is a hand-held key ring having an appropriate array of finger tip switches 12-16, in acase 50 which can include akey ring 52 on aswivel connection 54. The hand-heldcase 50 is retained by the operator of the vehicle so that as the operator approaches the vehicle signal S can be transmitted to receiver unit R by merely depressing one of the finger operated switches 12-16.Antenna 36 is provided on a PC board incase 50.

In the preferred embodiment, receiver R includes adetector 60 tuned to approximately 310 MHz so that a signal S is received byantenna 61 printed on a PC board of the receiver,detector 60 recognizes the frequency and allows the first portion of the signal to pass throughline 62. This is the initiate or signal recognizing line for activating power upcircuit 64 having anoutput 66 for directing logic power tomicroprocessor 80, such as 5.0 volts.Detector 60 includes a filter for removing the 310 MHz carrier so that the output data inline 70 includes a plurality of spaced, logic conditions in pulse form which pulses are directed to the serial input ofmicroprocessor system 80 for processing after the microprocessor has been activated by the voltage inoutput line 66. The voltage in line 66 (V_cc) is monitored bylow voltage circuit 68. If the voltage drops to about 3.5 volts,microprocessor 80 is reset byline 69 becauselogic 1 may not be easily recognized. As indicated, after 4.0 seconds, or another selected time, power inline 66 is turned off awaiting the next coded signal recognized by logic inline 62.

Microprocessor 80, as didmicroprocessor 10, includes a preprogrammed PROM together with an appropriate RAM for processing information in accordance with the system parameters of the present invention. Anoscillator 82, similar tooscillator 32, drives this microprocessor and other circuits of the receiver. In accordance with an aspect of the invention,

oscillators

32 and 82 are set to the same frequency; however, they are not matched and are not crystal controlled. Thus, the frequency of these two oscillators can be different within a relatively narrow range which could affect sensitivity of the receiver R to the coded received signal S fromtransmitter T. Microprocessor 80 of receiver R is calibrated to compensate for variations between clocking

oscillators

32, 82. When stating that the two clocking oscillators are set to the same frequency, this concept indicates only that the frequencies of these two oscillators, when taken together with the processing performed by the

microprocessors

10,80, produce the same general data transmission and data recognition. The actual oscillator frequencies could be different to still be generally matching in this context, such as by using different dividing networks. Calibration of the receiver will be described later in connection with FIGURE 13.

To load a code into receiver R,microprocessor 80 includes a program enableline 84 groundable by manual manipulation ofswitch 86 mounted in the vehicle. The function and location of this switch or other terminals are known to the manufacturer and the dealer. By closingswitch 86,microprocessor 80 is shifted to the code loading condition wherein identification codes or security codes contained in signals S can program receiver R in a manner best explained later in connection with FIGURES 2 and 3. Binary data, in serial form, ondata bus 90 from the microprocessor includes only the identification code or security code portion of a transmitted or received signal S. Whenswitch 86 is closed, a selected logic inline 92 represents a WRITE signal for writing the binary logic of the security or identification code indata bus 90 into a EEPROM or custom integratedcircuit 100. If the logic online 92 is not the WRITE signal, the binary data onbus 90 is compared with the existing security codes or identification codes in theintegrated circuit 100 to produce an appropriate compare designation signal inoutput line 94 which is communicated withmicroprocessor 80 to be processed into an indication that the coded portion of the receive signal S corresponds with one of the identification or security codes loaded in the registers ofintegrated circuit 100. As will be explained later, integratedcircuit 100 includes an enablebit 110, which bit is set at the factory to allow programming by grounding thefield program line 84. Enablebit 110 ofcircuit 100 is not set when receiver R is shipped to the automobile manufacturing or assembly plant and can be set only by a specially designed machine available to the manufacturer of the control system or by a designated company, such as the automobile assembly plant. Whenever this bit is not set, the signal inline 92 has no effect upon changing the logic of the registers contained in the code registers ofcircuit 100.

All of the circuits shown in FIGURE 1 and so far discussed are somewhat standard solid state micro-chip components or are custom integrated circuits which can be produced using standard technology for accomplishing the defined functions. Power upcircuit 20 controls the small batteries (5.0 volts) intransmitter T. Circuit 64 of receiver R directs power to the rest of the circuits in receiver R whencircuit 64 is initiated by closing one of the switches 12-16 intransmitter T. Detector 60 includes a pass filter for the carrier frequency and a circuit to remove the carrier to create the envelope in data bus orline 70.Microprocessor 80 transfers only the identification or security code frombus 70 toline 90. The function portion of the code will be decoded inmicroprocessor 80 for the purpose of supplying actuation signals throughload drivers 120 to

appropriate outputs

122, 124 and 126 for the purpose of selectively operating previously identified mechanisms B, C and D. The B+ voltage fordrivers 120 and relay 130 is the battery voltage for the vehicle onto which receiver unit R is mounted. If receiver R is mounted in a home or other building, the B+ voltage for the load drivers, etc. could be provided by an appropriate transformer, driven by the house voltage with a back-up or stand-by battery. This completes the general description of the preferred embodiment illustrated in FIGURES 1 and 1A.

Referring now to FIGURE 1B, creation of a transmitted signal S by the transmitter is schematically illustrated. When one of the selector switches is closed,microprocessor 10 is powered up. The microprocessor then reads the switch and reads the identification or security code stored permanently in a custom integratedcircuit 40, shown in the transmitter portion of FIGURE 1. This integrated circuit has a single twenty-four bit register for storing a single unique code, which code is loaded into the register when transmitter T is manufactured. This code is unique and is not duplicated from one transmitter to the next. An appropriate program enableline 42, similar toline 84 of receiver R, allows this single register to be loaded with a random binary number generated by an appropriate number of generating devices. This code generation is gone by serial loading from anumber generator 44 throughline 46 as shown in FIGURE 1. Other random number generators can be used.

In the preferred embodiment, a known universal code is loaded into a control transmitter to be used at the factory for testing each receiver R shipped to the factory and after the receiver is mounted. All registers incircuit 100 of each shipped receiver R are preset to this known universal code. Consequently, all receivers and control transmitters sent to the factory have the same universal code. Each transmitter has its own unique code. The advantages and details of this concept will be described later.

After reading the unique transmitter code, as indicated in FIGURE 1B, the unique code is loaded into RAM and the function of the depress switch is also loaded into the appropriate RAM ofmicroprocessor system 10. Thereafter, the microprocessor system outputs an initiation signal or wake-up code which is generally over two bits of data, the identification or security code, which is usually twenty-four bits of data and the function code which may be eight bits of binary data. The initiation or wake-up signal is asteady logic 1 for two or more bits and is contained insignal 38 as shown at the bottom of FIGURE 1.Signal 38 is directed by the line with the number to the input of ANDgate 39 for the purpose of controlling the output ofoscillator 30 used to create transmitted signal S. Signal S is then received byantenna 61 for processing by a receiver R.

In accordance with the present invention, the custom integratedcircuit 100 of the receiver includes preprogrammed operating characteristics which are essentially memory locations that can be programmed electrically using standard EEPROM technology. The integrated circuit includes several storage areas for twenty-four bit binary information. FIGURE 2 shows these storage areas as registers in an EEPROM. The security codes in these registers are processed by various logic circuits some of which are shown as being contained within the architecture ofcircuit 100; however, these logic processing components can be located in any IC component of the receiver and even be performed by the program of themicroprocessor 80. The logic processing concepts illustrated in thecircuit 100 facilitate description of the operation of receiver R as it relates to the stored identification codes in both the READ mode and WRITE mode. Data onbus 90 is controlled by the coded portion of the signal ondata line 70; however, it is converted to a binary logic after thelogic 1 andlogic 0 conditions have been identified and formed with proper calibration. This pure binary data is stored intoregister 102 of the EEPROM. In the preferred embodiment,logic 1 is greater than 2.4 volts andlogic 0 is between 0.0 volts and 0.4 volts. Binary data onbus 90 can be parallel loading or serial loading. This loading occurs any time that a code, recognized as a security code, is received byunit R. Oscillator 82 can be used to clock the received security code intoregister 102, irrespective of the READ/WRITE logic online 92. After a security code has been received and stored incircuit 100, the stored code is compared with the identification or security codes stored in twenty-four bit registers I, II, III -- N. Any number of security code registers can be employed incircuit 100; however, in the preferred embodiment, only two registers I, II are provided. The binary logic stored inregister 102 is directed, in parallel fashion, through twenty-four data lines, identified jointly asline 200, to a twenty-fourbit comparator 202. It is appreciated that the comparator may be programmed into the microprocessor itself or provided hardwired in an IC. Indeed, register 102 could be in the microprocessor itself with the data in registers I-N being transferred to the microprocessor for comparison with an incoming security code. When a code is received from thebus 90, an enable command can be created to sequentially output the logic in registers I, II, III - N through schematically illustratedlines 212. If one security code in the twenty-four bit registers matches the code stored inregister 102, a compare signal is created inline 94. This signal indicates that the code portion of the received coded signal S matches logic stored within an area or register ofcircuit 100.

Circuit 100 is used for two or more twenty-four bit registers I-N, which registers may be changed after enablebit 110 has been set (as will be explained later) and a WRITE signal is created inline 92 by groundingline 84. An erasable PROM allows the storage of identification codes and subsequent file programming. The Executive Program of the microprocessor, which can include much if not all of the data processing functions, is fixed into the PROM of themicroprocessor chip 80. Consequently, the comparison network and procedures can be accomplished in either themicroprocessor 80 or in a custom IC chip, as schematically indicated generally in FIGURE 2. Upon a COMPARE signal appearing inline 94, the particular load driver indriver network 120, shown in FIGURE 1, is actuated to energize mechanism B, C or D, according to the

switch

12, 14 or 16 which has been closed to create the transmitted function portion of signal S.

Should an identification or security code be loaded intoregister 102 either incircuit 100 ormicroprocessor 80 while a WRITE signal is valid atcircuit 100, the twenty-four bit registers I, II, III - N will be changed to correspond with the new security code inregister 102. As the code transmitted to receiver R remains inregister 102 or is stored elsewhere, the enablenetwork 208 simultaneously or in sequence parallel loads the twenty-four bit code fromregister 102 to the twenty-four bit registers shown in FIGURE 2. Loading of the code is illustrated by

lines

210, 220 of FIGURE 2. Simultaneously loading or sequence loading is controlled by sequencingline 210. A register is loaded upon receipt of a signal at the E terminal byline 208. This loads each of the registers with the received code inregister 102. In the preferred embodiment only two twenty-four bit registers are employed; therefore, the first code stored inregister 102 when the WRITE signal in line 22 is valid is loaded into both registers I and II. Upon acknowledgement in the microprocessor of a second new code, different from the code stored inregister 102, the second new code replaces the first new code inregister 102. If this happens before the WRITE signal inline 92 has expired or becomes invalid, the next, new stored code is loaded into all registers subsequent to register I. Consequently, the second new code received during a single WRITE command will be loaded into twenty-four bit register II, twenty-four bit register III, etc. Upon receipt of a third new identification code, the same process is repeated, with the sequence network or control 208 loading the third new code into twenty-four bit register III, and any subsequent registers incircuit 100. This process can continue until all registers are filled with a separate and distinct, new identification code; however, all of this loading procedure, or field programming, must occur during a single WRITE command caused by manually groundingline 84. As will be explained later, the WRITE signal remains for a preselected time, such as 30 seconds. Each of the separate and distinct, new identification codes is obtained by using a different transmitter T, each of which has its own unique and, thus, different identification or security code ramdomly loaded at the factory making the transmitters. In this manner, the security code or identification code incircuit 100 is loaded by a procedure involving the grounding ofline 84 and depression of one of the buttons or switches 12-16 on any transmitter T. This easy procedure causes the first new code to be loaded into all designated areas or registers ofcircuit 100. A second transmitter T can be actuated by depressing one of the function buttons or switches 12-16 to program a second new code incircuit 100 of receiver R. This second new code is loaded into the register with the next significant level, and all subsequent registers with lower significance. The advantage of using this overwrite logic procedure is that if an unauthorized person, having an easily obtainable transmitter T, desired to surreptitiously record a new transmitter code into someone else's receiver, only one new code will remain in the receiver. Consequently, the authorized transmitter will no longer operate the receiver. If an authorized transmitter does not function, it will be readily apparent that the receiver had been the subject of tampering. By using this scheme, an unauthorized transmitter cannot be used to store a code in a subsequent register ofcircuit 100. All loading occurs during a single WRITE command signal. In practice, the command has a duration of approximately 30 seconds to assure that only authorized transmitters load identification or security codes into the twenty-four bit registers ofcircuit 100.

The flow chart for field programming of a receiver is laid out in FIGURE 3. An acknowledged code is received and stored inregister 102, as previously discussed. It is then necessary to determine whether or not this is a new code, by anappropriate circuit 230. This can be done by determining if a COMPARE signal was created inline 94. If this signal is not created, the code inregister 102 is new. The code is READ bycircuit 100 as indicated byline 222, stored, compared and identified by the logic inline 94. Then the condition of the READ/WRITE line 92 is interrogated. If such interrogation, indicated bycircuit 232, is negative, the code inregister 102 is not valid and the process is terminated. Whencircuit 232 provides an affirmative response, this response is transmitted inline 240 to a timing stage. This initiates asoftware timer 232, which in practice has a duration of approximately 30 seconds. As long as this timer stage is not timed out,line 244 is active to initiate the code loading means 250. This stage or circuit loads a first new code which is the first new code stored inregister 102 during the time ofstage 242. Code loading means 250 has a first stage that is enabled for a time, such as 10.0 seconds. A second stage of loading means 250 is identified as circuit orstage 252 and is also enabled for a given time, such as 10.0 seconds. The given time of thesecond stage 252 is initiated upon a loading affirmed signal inline 251 from the first stage of code loading means 250. Within the second ten seconds stage, a second new code, i.e. code B, can be stored inregister 102 and then loaded into all registers I-N, except register I. This procedure can be repeated for at least one additional stage as indicated byline 252. This next stage lasts for a time, such as 10.0 seconds, after code B is loaded into the registers subsequent to register I. Should more registers be employed,timer 242 would be increased by approximately ten seconds for each additional code to be loaded into a register available incircuit 100. It is appreciated that the twenty-four bit registers I-N are really only storage areas of a EEPROM memory and need not be constructed in any particular architecture. As soon astimer 242 times out,line 246 resetscircuit 230 for preventing programming untilcircuit 232 andtimer 242 are again activated. In this manner, an unauthorized person cannot write into the lower registers ofcircuit 100 at some later time; however, sufficient time is available for field programming of receiver R by two or more authorized transmitters.

Whenever a signal is received byantenna 61, power is maintained for 4.0 seconds on theline 66. If a shorter time is created bycircuit 64, a second circuit holds the power until field programming can be accomplished, i.e. at least 30 seconds or power is maintained as long asline 84 is grounded.

In FIGURE 3A, there is a schematically illustrated scheme for comparing a new code inregister 102 to existing codes in registers I-N as called up byline 222 of FIGURE 3. The code is first compared to stored code A. If there is a match, a valid command is created inline 94. This procedure progresses from code A to code B, etc., through all registers incircuit 100. FIGURE 3B illustrates a schematic circuit concept for accomplishing the time delay discussed in connection with timer ortiming program 242 started upon identification of a new incoming code. When thefield programming switch 86 is closed,line 84 is grounded as previously discussed. This can actuate a oneshot multivibrator 242′ set at approximately 30 seconds. Consequently, alogic 1 WRITE signal is created for thirty seconds inline 92. A new code received during this time initiatesline 230a, illustrated in FIGURE 3, which initiation signal is combined with the WRITE signal by ANDgate 248 for the purpose of enabling the network E, i.e.circuit 208 of FIGURE 2. This network, under the Executive Program of the microprocessor, loads the twenty-four bit registers incircuit 100 as discussed in detail earlier.

FIGURE 3C is an architecture that can be used to correlate loading of successive new codes A and B during field programming. During the first stage of the code loading means 250, the inputs ofgate 249 areline 249a, existence of the code A, andline 249b, the ten second window from the first stage of loading means 250. This logic is combined by ANDgate 249 for loading all registers by enablinglines 210 I-N. when the time of the first stage expires, flip-flop 254 is toggled to initiate thesecond time stage 252 for the purpose of recording code B in all registers after register I. As can be seen, in the scheme so far described in FIGURE 3C, if a transmitter is not actuated during the first stage, code A will be loaded into subsequent registers leaving register I with a prior code. To prevent this from happening, D terminal flip-flop 252 is connected to the output of ANDgate 249. Unless all registers are loaded during the first stage, subsequent stages cannot be loaded. Other arrangements could be employed for accomplishing the field programming of the preferred embodiment of the present invention. The circuitry illustrated in FIGURES 2, 3A, 3B, 3C are illustrative architecture to teach the inventive concepts.

Various arrangements can be employed for identifying the function portion of signal S that operatesdrivers 120 in accordance with the depressed switch 12-16 of transmitter T. FIGURE 4 illustrates schematically an arrangement in receiver R for accomplishing this purpose. When an incoming code is loaded inregister 102, the logic inline 102a (FIGURE 3) is combined with a valid COMPARE signal inline 94 to toggle flip-flop 60. Wheninitiation circuit 64 expires, register 102 is reset and the logic inline 102a is shifted to a logic, such aslogic 0. This enables adecoder 270 for transferring the logic bits stored infunction register 262 to the input lines ofload drivers 120 for operating the logic on

lines

122, 124 and 126. An enable signal inline 264, upon receipt of a coded signal, loads the function portion of the signal intoregister 262 for decoding bydecoder 270. All of this logic is performed by the Executive Program stored inmicro-processor system 80. Of course, other arrangements could be employed for identifying and outputting the proper function upon identification of the proper security code in the code portion of a received coded signal S.

The flow diagram of FIGURE 5, divided into sections 5A, 5B and 5C, illustrates the concept of the present invention from assembling receiver R into a motor vehicle at a factory and programming the receiver at the dealer or later by any transmitter T having an unknown, but unique identification or security code loaded therein. Progression through this flow diagram will describe the function of the invention together with several advantages obtained by using the invention, as so far described in connection with FIGURES 1-4. Receivers R are loaded with a specific universal code in all registers ofcircuit 100 and are then shipped to the automobile manufacturer. At the assembly line, indicated to be the "trim area", a receiver is installed at an appropriate location within a vehicle. Seeblock 300. A special control transmitter Tc contains the special universal code "T" in itscode register 40. When transmitter Tc is actuated at the trim area, by closing one of the switches 12-16, as indicated byblock 302 the door locks or trunk latch can be tested. Activation of the door locks and latch indicates that the receiver being tested is operating properly. This test is done by transmitter unit Tc. Should the function test, indicated byblock 302, be successful, a worker on the assemblyline then grounds enableline 84 by closingswitch 86 or otherwise, as indicated byblock 304. There is then a five second delay which is processed bymicroprocessor 80 and indicated byblock 306. To indicate that the enable line is actuated, the microprocessor of the receiver operates the door locks, as indicated byblock 308. This sets theprogramming timer 242 awaiting loading of a new code fromregister 102 to registers I-N, as shown in FIGURE 2. This concept is best described in connection with FIGURE 3B. Then the worker actuates standard transmitter Tc adjacent the assembled receiver R, as shown byblock 310. As long as a signal from transmitter Tc has not been received, an output remains inline 312 and no signal is given inline 313. If the thirty seconds oftime 242 has not expired, theoutput 322 ofblock 320 is negative indicating the system is still awaiting actuation of the standard transmitter Tc. Consequently, there is a waiting loop which is held for thirty seconds awaiting receipt of a code T. If there is no such signal received for the loop time, i.e. 80 seconds, the timer expires as indicated byblock 330. Theprogram enabling bit 110 ofcircuit 100 is not set, as indicated byblock 332. To set the essential bit, the operator or worker must remove the ground ofline 84 and start the process over fromblock 304 as indicated byline 346. Of course, if grounding of the enable line actuates one shot 242′ as indicated in FIGURE 3B, the ground is removed automatically upon expiration of the one shot thirty seconds. This function is indicated byblock 340 to represent a condition when a code T has not been received during the lapsed time of thefield programming timer 242. With either concept, the operator or workman must recycle the factory enabling step by again groundingline 84. Various arrangements can be used for groundingline 84 to create a WRITE signal atcircuit 100 of the installed receiver R. This enabling step assures that the universal code is in the receiver until the desire to reprogram the unit; consequently, testing atblock 302 can be done with transmitter Tc.

Assuming that during the time loop, indicated between

lines

312 and 322, there is received and acknowledged code T at the receiver, enablebit 110 is then set as indicated byline 313actuating block 350. The microprocessor, when the receiver is enabled, again cycles the door locks to indicate that enablebit 110 has been set. This function is indicated byblock 352. The ground online 84 is removed as indicated byblock 354. If this release of the ground has not been done by a positive step or by expiration of oneshot 242′, there is a processing loop indicated byline 356 and block 358. As soon as the ground has been removed, receiver R is properly conditioned for field programming and remains with the vehicle as it progresses through the assemblyline and is delivered. The vehicle is then shipped to a dealer where a transmitter T is supplied to the customer with the vehicle. This completion of factory involvement in use of the invention is indicated by the dashedline 360 from FIGURE 5A to FIGURE B.

buttons

12, 14 and 16 in sequence. This is a testing function indicated byblock 472. If there has been a second receive code (code "B"), then the second code is stored in register B (I), as indicated byblock 480. When that second programming occurs, themicroprocessor 80 actuates the door locks again, as indicated byblock 482. Then the ground online 84 is removed.

Blocks

470, 472 are cycled.

When a new transmitter is used to reprogram the receiver of system A, the new code of the new transmitter is loaded into all twenty-four bit registers ofcircuit 100. This erases any previous identification code or security code within the registers. Consequently, unauthorized reprogramming will negate the functioning of the original transmitter or transmitters. In this fashion, reprogram is detected at once and can be corrected by immediately changing the program back to the original codes "A" and/or "B", by using the original transmitter or transmitters. Should a transmitter be lost, it is only necessary to purchase a new transmitter and then reprogram the receiver in the field. At no time is it necessary to buy, readjust manually or repair a receiver which is fixedly mounted in a vehicle.

FIGURE 6 is a schematic view illustrating the concept of creating the load release signal inline 500 to set enablebit 110 of the EEPROM. This is accomplished by groundingline 84 throughswitch 86, as previously described. At the same time, the T code is transmitted and loaded intoregister 102 where it is compared to the registers and produces a signal inline 94. This is the second input to ANDgate 502 which has invertedinput 504 fromswitch 86. This drawing is schematic in nature and is used to illustrate the operation of the invention upon receipt of the code T at the same time that line 84 is grounded or during a held time, as represented by oneshot 242′. This occurs atblock 304 of FIGURE 5A. The enable bit 110 ofcircuit 100 is set by a command inline 500. In this manner, the receiver in the vehicle is permanently released for field programming. Thebit 110 is released or set at the facility manufacturing the receivers for the purpose of initial loading of the T code into all registers ofcircuit 100. Thereafter,bit 110 is reset to lock code T in receivers at the factory to facilitate field programming by a randomly selected transmitter.

FIGURES 7-13 illustrate a further aspect of the invention wherein a particular type of binary code is employed for the transmitted signal S. In addition, there is provided a unique arrangement for calibrating the operation of the receiver so thatmicroprocessor 80 driven byblock 82 will be locked onto the output characteristics ofmicroprocessor 10 driven byoscillator 32, without a need for the two oscillators to be matched and/or crystal controlled. FIGURE 7 is a simplified view of the system shown in FIGURE 1 illustrating only those items needed to consider the signal processing aspect of the invention. In FIGURES 8 and 9 the pulse length W is a "window" for each bit of data in the transmitted signal on a high frequency carrier. The initiation portion of the signal S includes aconstant logic 1 with a duration of at least two windows. As soon as this signal is received bydetector 60,microprocessor 80 is initiated and awaits the following portion of the coded signal S which is communicated in binary language throughdata bus 70 fromdetector 60 tomicroprocessor 80. In accordance with one aspect of the invention, the binary number on each bit or window is represented by a duty cycle, i.e. as a percentage of the bit or window length. The window length or bit length is the distance between two adjacent positive going, leading edges of signal S. Thelogic 1 in signal S is a duty cycle indicated to be 80% of the width of the window. In a like manner, thelogic 0 has a duty cycle of 20% of the window. By using positive going pulses for bothlogic 1 andlogic 0, they are more easily detectable and easily processed by the receiver. The procedure for processing the incoming received security code portion of signal S is illustrated in FIGURES 10 and 11. In accordance with the illustrated embodiment of the invention,sampling pulses 600 are created simultaneously with the incoming logic ondata bus 70. The number of sampling pulses is selected to represent a given relationship in the bit length or window W. In practice this is about 30 sampling pulses during each window W. These sample pulses or signals are created by a samplingpulse forming circuit 610 driven byoscillator 82.Circuit 610 involves a divider circuit for the output ofoscillator 82 to create approximately 30sampling pulses 600 during a window W. Alevel sensor circuit 612 is clocked by theoutput 614 of the samplingpulse creating circuit 610. During eachsample pulse 600, alogic 1 appears inoutput 616 oroutput 618, in accordance with whether or notdata line 70 is at high level or at a low level, respectively. The sampling pulses appear inoutput 616 when the data is high. These sample pulses are counted bycounter 620. The count ofcounter 620 is compared to a set upper limit X bycircuit 622. If the assumulated count exceeds X, alogic 1 appears inline 624. If at the end of the window or bit,counter 620 does not exceed X,circuit 622 is reset and alogic 1 appears inline 626. Assume thatline 624 does shift to alogic 1,circuit 630 will load alogic 1 intoregister 102 upon receipt of a load signal inline 632. Should alogic 1 appear inline 626, and alogic 0 inline 624, whencircuit 622 is reset, the state of the bit may be questionable in some higly unusual circumstances. Thus, a signal inline 626 is not interpreted as alogic 0 in the window W. Thus, further circutry is employed to determine whether or not alogic 0 should be set into theregister 102. This additional circuitry is employed to be certain of the logic to load into each bit ofregister 102.

FIGURE 11 shows an arrangement for determining whether or not the borderline case whencounter 620 does not reach X is alogic 0 or alogic 1. This is accomplished by using an appropriate circuit, such as D-type flip-flop 640 which is clocked upon receipt of alogic 1 inline 626. The D terminal of the flip-flop is connected to theoutput 650 oflimit detector circuit 660. The limit of this circuit is set to a number Y substantially corresponding to 1/3 of a window in the preferred embodiment. Counter 662 counts sampling pulses occurring while data line 70 is at a low level. If the count incounter 662 exceeds the number Y, then the bit in the window W is alogic 0. Alogic 1 appears inline 650, so that alogic 1 inline 626 clocks flip-flop 640 to apply alogic 1 at theQ output 670 and alogic 0 at theQ output 672. This causes alogic 1 to appear in the "logic 0"circuit 674 and deactivates the "logic 1"circuit 630; therefore, a "load bit" signal inline 632 loads alogic 0 into thecode register 102. To determine the length of window W, i.e. the bit length of Signal S, the circuit illustrated in FIGURE 11 includes aleading edge detector 700. One-shot 702 disablesinput gate 704 ofdetector 700 so that spurious leading edges, such as spikes, will not be detected. The one-shot is set to a time which is a relatively high percentage of the anticipated sampling pulses during a window W. In this manner, leading edge detection occurs only on the positive going portion of data online 70. This will read the binary logic during each of the successive windows W in the 24 bits forming an identification or security code.Output 710 resets counters 620, 662 and resets setlimit circuit 622. This output creates the "load bit" signal inline 632 through a short time delay network orcircuit 712. By using the delay, a digit ofregister 102 is loaded for each window or bit immediately after the binary logic of the window has been determined in an appropriate manner as suggested by the circuit in FIGURE 11. In operation, counter 620 counts until alogic 1 appears online 624 if the bit is alogic 1. This logic loadscircuit 630 and thus, applies alogic 1 at the bit location inregister 102. Upon the next leading edge indicating the end of a window W, a "load bit" signal inline 632 shifts thelogic 1 fromcircuit 630 into the first location ofregister 102. Should alogic 1 not appear inline 624, then counter 662 is relied upon to count the sample pulses during low level of the data online 70. If this count exceeds Y, alogic 1 appears inline 650 indicating that the binary logic for the existing window W is alogic 0. This applies alogic 1 to the D terminal of flip-flop 640 so that upon reset of circuit 622 alogic 1 is clocked intocircuit 674 into theQ output 670 of flip-flop 640. This applies to alogic 1 in "logic 0"circuit 674. Immediately thereafter a "load bit" signal inline 632 loads alogic 0 into the next bit position ofregister 102. After this loading has been accomplished for all bits inregister 102, the content of this register is compared to the previous coded signal received by the receiver which is contained inregister 720. If there is not a comparison, then a "new" code is recognized bycomparator circuit 722 which generally corresponds withlock 230 in FIGURE 3. This is an alternate arrangement for identifying a "new" code and can be used. Of course, after a code is received, a timer can be used toempty register 102 so that any next code will be loaded in the register. By using the circuit shown in FIGURE 11 there is a positive identification of the duty cycle type data onbus 70 to protect against improper detection of transmitted codes. This concept provides a positive response by a receiver R, which adds to commercial acceptance of the system constructed in accordance with the present invention.

Referring now to FIGURES 12 and 13, another aspect of the present invention is illustrated wherein the receiver R is provided with an arrangement for matching the response detected by use ofoscillator 82 with the transmitted logic determined by theoscillator 32. To accomplish this calibration concept, the average width of the windows W, as detected bysample pulses 600 appearing inline 614, is determined. The average can be accomplished by a circuit illustrated in FIGURE 13, wherein leadingedge detector 700 produces a pulse inline 710 whenever a positive going leading edge is detected. Counter 800 counts thesampling pulses 600 during a given number of windows W, which in the illustrated embodiment is 24.Circuit 802 produces an output inline 804 when the 24 windows have been counted. Of course, the oneshot 702, shown in FIGURE 11, could be used to remove most noise or spike in the incoming binary data. A signal inline 804 loads register 810 with the count fromcounter 800. Immediately thereafter delaycircuit 812 resets counter 800 for the purpose of repeating the counting function. A dividingcircuit 820 divides the accumulated count inregister 810 to produce an average count for each window W. Two-thirds of this count is loaded intoset limit circuit 622 of FIGURE 11 to detect alogic 1. This number represents the count X ofcircuit 622. One-third of the average count incircuit 820 is loaded as the number Y ofnumber limit circuit 660. By utilizing this concept, the windows W are set to the transmitted window W of signal S. Other arrangements could be employed for accomplishing this same purpose; however, the particular binary coding scheme employed in accordance with the present invention facilitates this type of receiver calibration.

The present invention is basically described in connection with FIGURE 5 and the remaining circuits and flow diagrams are used to explain how this type of system can be constructed and is constructed to practice by using easily available principles. In practice certain other features and characteristics of system A have been developed. Signal S has used a 64 bit receiver wake-up signal followed by a customer identification code. This would allow each transmitter to be useful for a given producer of vehicles, but not for all vehicles employing a receiver as defined herein. A synchronizing pattern can be sent on signal S such as a high logic for 15% of a bit and then a low logic for 3.85 bits. This 4 bit portion synchronizes the receiver with the data to be thereafter transmitted on signal S. In practice, the function code is 8 bits with a given sequence selecting the device to be operated. Thus, by holding the unlock switch, all doors can be unlocked while a depression of this switch unlocks only the driver door.

Referring again to FIGURES 2 and 6, enablebit 110 is employed so that receivers R cannot be used unless a transmitter with a T code is available. Consequently, should the receivers be lost or displaced before assembled into a vehicle and subjected to a signal having a selected T code, the receivers would be of no commercial value.

Although there are several operating procedures for designating which function is performed byload drivers 120, other concepts could be employed. Forinstance switch 14, as explained, can be used to unlock only the driver's door or all doors. In practice a single actuation performs the former function, whereas two or more actuations ofswitch 14, within a final window will unlock all doors. This same procedure could be used for other switches to increase the capacity of the system without increasing the number of switches.