AU603782B2

AU603782B2 - Electro-magnetic lock

Info

Publication number: AU603782B2
Application number: AU67308/87A
Authority: AU
Inventors: Kevin Harris; Melvyn Arthur Johnson; Randell Lumbewe
Original assignee: AUSTRALASIAN ELECTRONIC SENTRY
Current assignee: AUSTRALASIAN ELECTRONIC SENTRY PTY Ltd
Priority date: 1985-11-21
Filing date: 1986-11-21
Publication date: 1990-11-29
Anticipated expiration: 2006-11-21
Also published as: WO1987003403A1; AU6730887A; EP0245385A1; JPS63501452A; EP0245385A4

Description

6 777- I PATENTS ACT 165 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE P100/0i Form Short Til: r Ar' 0, 37 7 8 nt. Ci: Application Number: Lodqied: Complete Specification-Lodged: Accapted: Lapsed: Published: Vrriority: :.Related Art: Name of Applicant: e .0 Address of Applicant: Actual inventor: 00 04 0 S* A 1 TO BE COMPLETED BY APPLICANT AUSTRALASIAN ELECTRONIC SENTRY PTY. LIMITED Shop 2, 128 Highland Aveniue, Yagoona, New South Wales, Australia MELVYN ARTHUR JOHNSON REVIN HARRIS RANDELL LUMBEWE 0 resU; o Srice, Peter Maxwell Associates, Blaxland House, Ross Street, NORTH PARRAMATTA N.S.W.

Completm SpecIfication for the Invention entitled: ELECTRO-MAGNETIC LOCK~ 2151 ig statement is a full description of this, inventin, inciuding the best method of performing it known josriptloo Is to be typed In doubie spacing, pica type face, In an area niot exceeding 250 mm In depth and 160 mm In S width, on tough white paper of good quality and It Is to be Inserted Inside this form.

Pr~ited by C Tom~dsoN, Commonwealth Government Printcr Canbera i i.il*L~;i;l~i;~i-r;i ii;ii_ i l.l _~-il-F

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I -2- This invention relates to locks and more particularly to an electromagnetic lock.

For the sake of brevity, the invention will be described in relation to an electronic lock for setting and releasing vehicle burglar alarms, but, it Is to be understood that the invention is not limited thereto so it may be employed in any situation where a lock is required.

Prior art electronic locks were developed to re-set car alarms without the driver first entering the vehicle und they embodied what may be termed a radio-frequency transmitter in the key.

Such radio frequency operated electronic locks suffer C* CS from a number of disadvantages not the least of which is that the code carried by the radio frequency signal could be v recorded by an unauthorised third party, stationed some distance from the car, who could re-transmit the coded signal when the vehicle was unattended to de-activate the alarm.

Furthermore, the receiver within the vehicle could be jammed by a signal from another transmitter operating at o' near the ed same frequency.

The above disadvantages could be overcome by changing J the transmitting medium of the coded signal to infrared or electromagnetic means. These mediums would be effective because they reduce the radiated range of the transmitter key and hence the receiver lock sensitivity and range.

2C -3- But to date no electronic lock has been devised which overcomes another disadvantage that the code (being digital in nature) carried by the transmitting medium could be identified by use of a sequencer adapted to count through every permutation of the code to disable the alarm. This means transmitter key/receiver lock systems cannot be used in higher security installations.

There is, therefore, a need to detect whether or not some form of code breaking is taking place and the system devised to fulfil that need has to be free of any chance of being accidentally triggered to give a false alarm.

This cannot be accomplished with radio frequency key systems due to the distance the coded signal is radiated. If

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another receiver lock (set to a different code) was located within range of the designated receiver lock then it would incorrectly assume an attempt to break its code has occurred.

Infrared systems require an optical pick-up device which must S f be exposed to the key holder, hence subject to the elements and to vandalism. A car windscreen could, of course, protect *.ed the optical sensor for automotive installations.

According to the invention there is provided an electromagnetic locking system comprising: an encoder transmitter having means for providing a digitally derived data code, means for generating a pulse-width modulated magnetic signal of a fixed frequency, at encoder for (04 -4coding the pulse-width modulated magnetic signal with the said data code, means for radiating the coded, fixed frequency, pulse-width modulated magnetic signal, (ii) a normally locked decoder receiver having means for receiving a coded pulse-width modulated magnetic signal, circuit means for deriving the data code from the received coded magnetic signal, means for comparing the received data code with a preset data code of the encoder "transmitter, means for processing the received data code only if it corresponds to the preset o data code to unlock the decoder receiver, and means for rendering the processing means S"16 inoperative in th< event that the received data code does not correspond with the preset data code.

o'oo In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings in which:- Fig 1 is a schematic diagram of an encoder transmitter of an electromagnetic lock according to a first embodiment of the invention, Fig 2 is a schematic diagram of a decoder receiver for an electromagn tic lock

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according to the first embodiment of the invention, Fig 3 is a schematic diagram of an encoder transmitter of an electromagnetic lock according to a second embodiment of the invention, and, Fig 4 is a schematic diagram of a decoder receiver for an electromagnetic lock according to the second embodiment of the invention, The encoder transmitter of the first embodiment of the magnetic lock of the invention shown in Figs 1 and 2 includes an encoding unit integrated circuit 10 to which is applied predetermined data rates and codes 16. The encoding unit .:a 1 is connected to supply line 12 and to earth point 17 through lines 18 and 19. Line 18 is the earth supply line while line 19 enables the encoder unit to transmit whenever power is supplied. A network of capacitor 20 and resistors 21 and 22 0 provides the correct timing for data rate transmission in *p respect of encoding unit 10. Capacitor 23 connected between supply line 12 and earth point 24 provides decoupling of the supply line 12.

The output from encoding unit 10 is used to control pulse oscillator unit 27 through line 25. Timing resistors 26 and 28 along with capacitor 30 set the frequency of oscillation while line 29 sets the oscillator unit 27 for a -6stable operation whenever encoding unit 10 output line 25 is high. Power for oscillator unit 27 is via line 12 and earth 17 via lines 18 and 31.

A light emitting diode 11 Indicates that the encoder transmitter is transmitting the encoded data. The oscillator unit 27 Is connected to a tuned circuit 13 having capacitive component 14 and inductive component 15. When the output of the coder unit 10 is high, the oscillator unit 27 is triggered to energise th6 tuned circuit 13 so that the series of pulses radiated by the inductive '.omponent 15 is in accord with the data rate and code ra.te set by the coder unit The pulsing alternating magnetic field radiated by the r encoder transmitter Is coupled magnetically to a tuned circuit 30 of the decoder receiver (shown in Fig. 2) set to :16 resonate on the same frequency. The tuned circuit 30 has capacitive component 31 and inductive component 32 which form a tank circuit that responds to the narrow band of the to*, alternating magnetic field signal.

Li If the frequency of the Incoming signal is correct, it O will be amplified by the Integrated unit 33 and the original data code will be recovered through the network formed by j diode 34, resistance 35 and capacitor 36.

The coded data is then fed to the decoder 37 which, If the code Is correct and In accor~dance with its Input produces a signal at its output 38. When this occurs, a positive voltage Is applied to an input of the Integrated -7circuit 39 so rendering integrated circuit 39 inoperative.

If the code is incorrect, capacitor 40 charges tc a preset voltage through diode 41. When this voltage has been reachd and ho output has been received from the decoder 37, the output 44 between terminal 77 and line 58 goes low to provide an alarm output signal to indicate that an attempted code break has occurred. Diode 42 is now forward biased and grounds the tuning circuit 30 stopping any further reception of codes until the capacitor 40 has discharged through resistor 43 to a predetermined value.

The time constant of the network formed by resistor and capacitor 40 sets the number of corrupt codes prior to lock out and the time constant of the network formed by a resistance 43 and capacitance 40A sets the lock-out period, I 'S Capacitance 46 may be reduced or removed to reduce the period of valid transmission at output 47 between terminal 77 and 78, In one form of the invention, the transmission time is set for 5 seconds and the lock-out time at 6 minutes.

It will be appreciated that the magnetically coupled alternating field does not require an aerial and as no radio i frequency carrier wave is used, a user licence is not U required. As a consequence of the use of magnetic coupling, the range of the system is small, say, of the order of centimetres.

The coded signal will penetrate any non-ferrous solid sch as the glass of a car window and the power requirements -8of the device are minimal.

The preferred frequency band is in the range of I to kilohertz but higher frequencies may be used. Although an identical word code may be used in another similar device, each of them will be immune from activatioij by the other.

Furthermore, the invention discriminates against casual tampering to reduce the nuisance value of false alarms from other users.

The alarm section of the lock will only respond for a predetermined period and only when the precise frequency is received. If, during this period, the correct code is f received the alarm sectio~n will not respond and the lock will S.*ee open. Thus, three components are required to operate the lock, namely:a) precise frequency of the alternating magnetic field b) data rate c) code word Figs 3 and 4 show a second embodiLment of the invention.

The encoder transmitter shown in Fig. 3 includes a digital encoding unit integrated circuit 110, to~ which Is applied a predetermined digital code 116.

5: The encoder 110 Is connected between supply lines III and 114 coupled to battery 115. There Is a switch 117 in line III* A network of capacitor 118 and vesistors 119 and 120 provides the correct timing for data ra, 'transmission in respect of the encoder 110.

H-9- The output from encoder 110 is used to control pulse oscillator unit 112 through line 125. Timing resistors 121 and 122 along with capacitor 123 set the frequency of oscillation while lines 126 and 127 sets the oscillator unit 112 for a stable operation whenever encoding unit 110 output line 125 is high. Power of oscillation unit 112 is via lines 111 and 114.

Thus, the digital encoder unit 110 is coupled to the pulse oscillator unit 112 which in turn is connected through resistor 124 to an inductive load circuit 113. When the 4 so* output of the digital encoder unit 110 is logic the pulse oscillator 112 Is activated to energise the load circuit 113 so that the series of pulses radiated by the inductive component 113 is in accor, with the data rate and Id data cod, as t by the digital coder unit 110, The putlsing magnetic fi I, radlated by the encoder transmitter of Fig. 3 is coupled magnetfcally to inductive co.aponent 128 of the decoder receiver shown in Fig. 4. The signal from Inductive unit 128 is referenced to earth point 179 and couple6 to first amplifying unit 134 via capacitor 1 04 129. Resistor 133 provides feedback to set the gain of this first stage. The output of first amplifier 134 is then fed too Into the second amplifier unit 137 via resistor 135.

Resistors 135 and 136 set the gain of this stage. Resistors 130 and 132 as well as capacitor 131 bias both amplifiers 134 NPPM cr and 137 for correct operation.

The output of amplifier unit 137 is then de-modulated by diode 138, resistor 139 and capacitor 140. This will reproduce the code originally sent by encoder unit 110 in Fig. 3. This signal is then buffered by unit 141 before being fed to decoder unit 180 if output 144 of integrated unit 147 is high.

The coded data is then fed to the decoder unit 180, which if the code is correct in accordance with its own preset input code 154, and the rate is correct as set by j resistors 151 and 152 along with capacitors 150 and 153, f produces a signal at its output 155. When thil occurs, a positive voltage is applied to an input of the integrated !j unit 159, enabling the output of unit 159 to cause transistors 166 and 167 to be activated via resistors 164, 168 and 170 along with transistors 165 and 169, dependant on the application of the lock. Capacitor 160 and resistor 161 ensure the integrated unit 159 is in the off state at original porer up. Resistor 162 and capacitor 163 form a m.'2 delay before resetting integrated unit 159 as we'~ as 4 I 8 integrated unit 147 via diode 181.

If the received pulse modulated digital code is *J received incorrect, i.e. not matching that which the lock has been pre-programmed, then no reset pulse to integrated unit 147 from integrated unit 159 via diode 181 will be forthcoming. After a preset time of invalid codes has been received capacitor 148 will charge via resistor 143 and enable integrated unit 147.

n- -11- This in turn will set NAND gate 156, triggering an audible alarm 171 via resistor 173 and transistor 172, as well as a visual alarm 174 via transistor 175. This alarm state will remain until capacitor 168 charges via resistor 157 and resets the NAND gate 156.

If integrated unit 147 is enabled tken further codes will be prevented from reaching the decoder unit 180 via output 144. The time of this is set by resistor 148 and capacitor 146, which will reset integrated unit 147.

Integrated unit 176 and display 177 are used for identification of key users dependent on the required application of the lock.

i' The time constant of the network formed by resistor 143 and capacitor 145 will determine the number of corrupt codes W prior to raising the -nvalid operator alarm, whilst the time S i constant of the network formed by resistor 130 and capacitor 129 will determine the time period that the invalid user alarm is activated, Resistor 148 and capacitor 146 determine the period during which signal processing will be inhibited.

It will be appreciated that as the magnetically coupled pulsing magnetic fi'ld does not require an antenna as no radio frequency carrier wave is employed a user licence is not required. As a consequence of the use of electromagnietic coupling, the range of operation of the system is in order of ten to twenty centimetres in any non-magnetic and shielded environment.

Kf .ft/ -V a .,all -12- The coded signal will penetrate any non-ferrous solid such as glass, brick, cement, acrylic and aluminium, but with reduced sensitivity.

The pulse modulating frequency of the encoder transmitter is approximately 1.0 kHz, higher frequencies may be employed, but it is dependant upon the component values of output transducer 113 and input transducer 128/129. The high frequencies may be employed however at the sacrifice of sensitivity.

There are three components that are required to operate the electronic lock of the second embodiment namely: a) the pulse modulating frequency, b) the rate at which data is being sent and c) the actual code itself, .5 As will be apparent from the above description, the invention is based on the premise that the receiver code performs three functions namely, a) to determine whether there is any serious so 0 attempt to crack the code, b) to initiate a time delay should the 0 receiver recognise any attempt to rrack the U code, this delay being programmable, 0 e S: dependant on the application. The delay ensures that code cracking by use of any form of sequencing would take an impractical time, together with the fact that this invention mst be activated at [1 ii

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41 10 ~m w- -13close range, fromr ten to fifteen centimetres, in addition, an audible alarm should be triggered to acknowledge a violation ha.s been attempted.

c) that the code be identikied as valid and the application lock is mad operational.

This electronic locking system may be applIed to any system to which power mnay be applied either via mains operation or by battery power, where a key and a lock are required. Further, this electronic lo.cking system may be applied to any application which requires operation by an identified and/or authorisedi user of another Jectronic or (electr.Lcal circuit.

Various modifications may be made to design and construction without daparting from the scope and ambit of the Invention.

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Claims

1. An electromagnetic locking system comprising: an encoder transmitter having means for providing a digitally derived data code, means for ,anerating a pulse-width modulated magnetic signal of a fixed frequency, an encoder for coding the pulse-width modulated magnetic signal with the said data code, means for radiating the coded, fixed frequency, pulse-width modulated magnetic signal, (ii) a normally locked decoder receiver having means for receiving a coded pulse-width modulated magnetic signal, circuit means for deriving the data code from the received coded magnetic signal, means for comparing the received data code with a preset data code of the encoder .4 transmitter, means for processing the received data code only if it corresponds to the preset data code to unlock the decoder receiver, and O means for rendering the processing means inoperative in the event that the received data code does not correspond with the preset data code.

2. A locking system according to claim 1 wherein the decoder receiver includes means operative upon receipt of the correct data code to activate or de-activate a further A, locking system.

3. A locking system according to claim 1 or claim 2 wherein the decoder receiver includes time delay means adapted to render the signal comparing means inoperative for a predetermined time.

4. A locking system according to any one of the preceding claims; and further including means for identifying valid users of the encoder transmitter.

A locking system according to any one of the pre'ceding claims and further including means providing a time delay operative to permit input signal processing to be readered inactive for a predetermined time upon receipt by the decoder of an invalid signal input code or invalid user identification.

6. A locking system according to any one of the preceding S claims and further including means for audibly identifying a 9 e received data code that does not correspond with the preset data code.

7. A magnetic locking system as hereinbefore described with reference to Figs. 1 and 2 and Figs. 3 and 4 of the accompanying drawings. S Dated this 28th day of August, 1990. CC 6. AUSTRALASIAN ELECTRONIC SENTRY PTY. LIMITED, Patent Attorneys for the Applicant: PETER MAXWELL ASSOCIATES 1 I4 N'