AU602336B2 - Improved security system - Google Patents

Description

iilii'i: I- rr^ 4U >>ASTRA1ALL Form PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. CI: 602336 Application Number: Lodged: S7F 7 3 y7z7, 4 4 Complete Specification-Lodged Accepted: Lapsed: Published: :Priority:

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This document contains the amendments made undr Section 49 and is cor:ect for printing.

Related Art: Name of Applicant: Address of Applicant Address of Applicant:

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4t TO BE COMPLETED BY APPLICANT CADIN ELECTRONICS PTY. LTD.

2a Cromwell Street, Burwood, Victoria, Australia DAVID NICHOLLS SANDERCOCK, SMITH BEADLE, Patent Attorneys 207 Riversdale Road, Hawthorn, Victoria, Australia Actual Inventor: Address for Service: Complete Specification for the invention entitled: IMPROVED SECURITY SYSTEM The following statement is a full description of this invention, including the best method of performing it known to me:- SNote: The description is to be typed in double spacing, pica type face, in an area not exceeding 250 mm in depth and 160 mm in width, on tough-white paper of good quality and it is to be inserted inside this form.

14166/77--L D r and year form signed Signature of applicant or Australian attorney Y C T"E ECT ON'ICS 'P TY TD S TO (Signature) SANDERCOCK, SMITH BEADLE THE COMMISSIONER OF PATENTS This form must be accompanied by either a provisional specification (Form 9 and true copy) or by a complete specification (Form 10 and true coov).

i~ 9*4 *4 #4ii 9 a 4 i 44 4b 9 44 94 49 4( 444 9 4# 00 49 2 TITLE: IMPROVFD SECURITY SYSTEM FIELD OF THE INVENTION This relates to improvements in security alarm systems for the detection and deterrence of unauthorised entry, fire, tampering and the like.

BACKGROUND OF THE INVENTION Security alarm systems are now widely used to protect domestic and business premises. One of the major problems with security alarm systems is the occurrence of false alarms which result not only in annoyance to neignbours but may endanger lives if remote notification, usually by means of a telephone dialler, to police, security organisation or an owner is effected. False alarms may be so persistent that the owner becomes afraid or embarrassed to use the system thereby completely negating the primary function of the system.

False alarms are usually quite random in nature and may be caused by taxi radio signals, CB radio signals, HAM radio signals and other occurrences. Prior art attempts to reduce false alarms included the use of pulse counting techniques which allowed the alarm to sound only after a number of pulses caused by an intrusion or the like during a given time. This technique may be applied either at the control unit or at the detector but leads to a reduction in the overall security offered by the system, particularly if the detector hes a low range or limited view of the area, thus allowing an intruder to enter without the alarm sounding.

Pulse counters may also hide the problem of a faulty detector even with control units which "memory latch" 870519, ltbspe.016,cadin.spe, j 3 previous alarms.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved alarm system in which the annoyance caused by false alarms is substantially reduced and which provides other features which improve the value of the alarm system to the user.

In accordance with the invention the7;e is provided an alarm system comprising: 9o 1Q40. a plurality of sensors each having means for providing a detection input signal arranged to cause activation of the alarm system; means for receiving a first detection input signal from any of said sensors; t means for inhibiting activation of said alarm system when said receiving means receives said first detection input signal; and means for removing said inhibition and allowing activation of said alarm system when said receiving raeans receives a second detection input signal from any one of said plurality of sensors at any time within a predetermined time of said first detection input signal.

In one embodiment, said alarm system includes a first alarm device adapted to be located essentially internally of the premises to be protected, a second alarm device adapted to a location centrally externally of the premises to be protected, said inhibition means causing activation of said first alarm device only, said second alarm device being activated if a further detect-')n input signal is received tbspe.048/cadin 90 7 6 I 3a I within said predetermined time.

In another embodiment of the invention, said alarm system includes means, such as a telephone dialler, adapted tu transmit an alarm signal to a remote location, said transmitting means being inhibited when said first detection input is received and being activated when a further 9,6 11 n O 0r 1 1, spe. CL I I 1- 4 1 detection input signal is received indicating that a false 2 alarm has not occurred.

3 In most cases, the alarm system wil 1 include at least 4 the internal and external alarm devices, although some systems will include only a dialler or direct communication 6 line without any alarm sounding devices.

7 In the present specification the term "alarm device" is 8 intended to include sounding devices such as speaker horns, 9 bells and the like, visual devices such as strobe lights and other special lighting systems, and combinations thereof.

11 It will be appreciated that the alarm system defined 12 above has the advantage of confining any inconvenience 13 caused by a false alarm to the interior of the premises 14 protected by the alarm system whereby the least possible annoyance to neighbours results. If the alarm is also 16 connected to a dial ler, activation of the dial ler occurs .4 17 only when the second alarm device is activated, that is, 18 only after a genuine alarm situation has beeii confirmed.

19 However, It should be appreciated that the dial ler aspect defined above may be used Independently of the external i 21 alarm inhibition system. In other words a separate dialler I 22 inhibiting device may be attached to an existing alarm 23 system to prevent the dialler operating when a false alarm 24 occurs.

The systems according to the present invention, operate 26 on the premise that false alarms are completely random in 27 nature, occurring primarily as one-shot or single break 28 occurrences, which are unlikely to be repeated within the 29 predetermined period selected fro;, detection of a further 870519, Itbspe. 016, cadin-sp,.

"Yl"r~lllrrUrp~.lrsyrri 5 intrusion. The predetermined period may be selected according to the requirements of the system but would normally be of the order of five or ten minutes. Since the system will activate the external alarm means when a further intrusion is detected, a real alarm situation will be likely to be detected since any movement of the intruder during the timing period will cause the whole system to be activated.

The system preferably includes means for activating the 09 dialler and/or the second alarm device in the event that the oaa 1Q.. initiating trigger lasts for more than a predetermined Qosa period, for example, five to ten seconds, such as would occur in the case of cut wires, tampering and the like.

Furthermore, the system preferably is arranged such that certain of the detection inputs bypass the inhibition means b and cause immediate activation of both alarm devices. Such inputs will usually include one shot devices such as mat sensors, narrow beam passive detectors, photoelectric detectors and the like, which are less prone to false claims.

Z0' Another source of false alarms occurs when the power supply to the alarm system is interrupted (or turned off) and the back-up battery voltage drops below the level at which the detectors will remain in the latche mode th.ereby causing a false alarm. In prior art alarms systems, there is no ability to deactivate the alarm system in the event that the power supply voltage drops below a predetermined level and in this situation a false alarm will always occur.

The invention also preferably includes a shut-down circuit provided to deactivate the alarm system when the tbspe.048/cadin 90 7 6 i /tbspe.048/cadin 90 7 6 5a voltage of the back-up f S S~ 048/caclin 9 90 7 6 6 1 power supply drops below a predetermined voltage at which 2 the alarm system will properly function, 3 In a preferred form of this a.pee6 of the invention, a 4 voltage comparator compares a reference voltage with the voltage at the mid point of a voltage divider connected 6 across the back-up battery. When the voltage across the 7 back-up battery drops below a predetermined voltage, for 8 example, 10.3 volts, the output from the comparator goes low 9 and cAusas the power supply to the alarm system to be turned off. In this way, the system is deactivated before the 11 voltage drops to a level at which the various detectors will 12 drop out due to insufficient voltage thereby avoiding 13 another source of false alarms.

14 The alarm system also preferably includes the following features which are believed to improve the usefulness of the 16 system to the user.

17 The system includes a mute button which reduces the a 44 4 18 voltage applied to the alarm horns and therefor the output 4 4t 19 from the horns for testing and for an initial 20 famil arization period. In one form, the volume of the 21 alarm horns is reduced to approximately one quarter of the ',4 .4 22 normal volume.

23 The system further includes a home mode in which the 24 alarm means are activated in the mute mode for an initial period, for example about thirty seconds, so that if the 26 system has been inadvertently activated, it will not be as 27 disturbing to the occupants of the premises or their 28 neighbours.

The system also preferably includes provision for 1519, tbspe.016,cadin.spe, 7remote radio signal activation. In this mode of activation, an acknowledging signal is additionally transmitted from the external alarm means.

Another problem with existing alarm systems is the tendency for external alarm devices and control boxes to be disconnected or destroyed thereby aborting any alarm function. Although it is possible to overcome this problem by the use of so-called satellite siren units which contain a rechargeable battery and siren generator in the same 1Q container, a further source of false alarms will occur in i the event that the mains supply is disconnected either due to power failure or other causes and the rechargeable battery gradually discharges to a voltage at which the siren will sound in the same way as if an attempt is made to disconnect or deactivate the satellite siren unit.

The invention also preferably includes a satellite alarm unit for a security system comprising an alarm means, power supply means and circuitry for detecting disconnection or tampering with said unit, and circuit means for detecting an abrupt change in the voltage supplied by the alarm control system to cause the alarm to be activated but which prevents activation of the alarm in the event that the voltage drops slowly, as would occur in the case of discharge of the remote power supply.

The alarm system further preferably includes first and second alarm devices arranged to have cyclic outputs which are X PL 1 i 048/cadin 90 7 6 8 1 out of phase by a predetermined amount.

2 In one preferred form said outputs are in excess of 3 1800 out of phase. This arrangement reduces the demand 4 placed on the power supply and improves the power supply regulation of the alarm system by reducing the instantaneous 6 drain on the power supply. The on/off ratio of each al;rm 7 device is also selected to facilitate better power supply 8 regulation and is preferably selected so as to be about 1:7.

9 A preferred embodiment of this aspect of the invention will be described in greater detail below.

11 BRIEF DESCRIPTION OF THE DRAWINGS 12 A presently preferred form of the three aspects of the r 13 invention defined above wil 1l now be described with reference j 14 to the accompanying drawings in which: Figure 1 is a block diagram of an alarm system 16 embodying the first and second aspects of the present 17 invention; 18 Figure 2 is a detailed circuit diagram of the alarm 19 system of Figure 1; Figure 3 is a block diagram of the first aspect of the 21 invention applied to a dial ler inhibiting device; 22 Figure 4 is a block diagram of an embodiment of the 23 third aspect of the invention, and 24 Figure 5 is a detailed circuit diagram of the circuitry of Figure 3.

26 DESCRIPTION OF THE PREFERRED EMBODIMENTS 27 Referring firstly to the block diagram of Figure 1 of 28 the drawings, the alarm system will be seen to comprise a 29 power supply section 1 to the output of which is connected a 870519, Itbspe. 016, cad in. spe, 9 1 current limited voltage regulator 2 which is adapted to 2 charge a stand-by battery and provide a voltage source 3 for the alarm system. A voltage divider network 3 provides 4 upper trip UT and lower trip LT reference voltages which serve as control ling inputs for a zone input comparator 4.

6 The output from the voltage regulator 2 is connected to a 7 shut down switch circuit 5 which ensures that the alarm 8 system does not remain operative when the supply voltage 9 from the stand-by battery falls below a predetermined level, in the present embodiment, 10.3 volts. To ensure that the 11 switch 5 does not repeatedly switch on and off as the S 12 current load from the battery during a power supply break 13 causes the voltage to rise, the circuitry of the switch 4 14 incorporates voltage hysteresis of the order of 0.7 volt. A voltage regulator 6 is interposed between the shut down 16 switch and the central micro-processor unit 7 and ancil1iary 17 circuits.

04 18 The micro-processor unit 7 is programmed to control al 1 19 timing, siren and announcement tones, LED driving and other S: w 20 switch selected functions. An in/out expander 8 is 21 connected to the micro-processor unit 7 to expand the 22 capabi lity of the micro-processor unit 7.

23 A mode switc,ing circuit 9 is also connected to the 24 micro-processor unit 7 to allow selection of various modes of operation either at the main control panel, at one or 26 more remote switches or by radio control.

27 The zone buffer/comparator circuit 4 includes inputs 28 from five different zones to be protected and a fire input.

29 Isolation switches 10 are provided to isolate any one of the 870525, Itbspe.016,cadin.spe, 1 five zones Z1 to Z5. In the present embodiment, zones Z4 2 and Z5 are reserved for use by one-shot devices such as 3 detector mats, photo-electric devices, narrow beam passive 4 detectors or the like.

Two separate alarm driving circuits are connected to 6 the micro-processor unit 7. In the present embodiment, 7 these circuits are connected to an internal alarm horn 11, 8 which is adapted to be located within the premises to be 9 protected, and an external alarm horn 12, which is located outside the premises to be protected. The alarm horns 11 11 and 12 are each provided with a muting circuit 13 and 14 4.

12 respectively, which cause the alarm horn to operate at a 13 considerably lower volume. The use of the mute function 14 will be described further below.

S15 Wher the internal and external alarm horns are sounding 9 I 16 together a large demand is placed upon the power supply. To 17 avoid the power supply regulation problems caused by this S 18 demand, the alarm horns 11 and 12 are driven by the micro-

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19 processor unit 7, so that their respective outputs are 1800 out of phase, as shown in the timing diagram In Figure 1.

21 To further improve power supply regulation, the on/off ratio 22 of each alarm horn signal is of the order of 1:7.

23 The micro-processor unit 7 is preferably in the form of 24 a programmed read only memory (ROM) which is suitably pro,grammed to achieve the necessary functions. More 26 particularly, the ROM is programmed to incorporate a false 27 alarm inhibition function which is designed to reduce the 28 inconvenience of false alarms to the user. This function 29 works on the premise that false alarms are completely random 870519, Itbspe.016,cadin.spe, L 11 o: #4 t4 4,* 4461 *Q 4 #4 ,4 94 d 4I 4 .l 04 4 *4 44 99 4 09I 4 4 *4Q 00 in nature and often appear as one-shot or single break occurrences. The micro-processor unit 7 is therefore programmed so that a first trigger from one of zones Z1, Z2 or Z3 causes actuation of the internal alarm horn 11 only and if a further trigger is received from any one of zones Z1, Z2 or Z3 or from Z4 or Z5, both of the alarm horns 11 and 12 will be activated. If no further trigger is received by the micro-processor unit 7, the internal alarm horn 11 will be deactivated after a predetermined time, for example, or 10 minutes as desired, thereby causing only limited disturbance to neighbours. It will be appreciated that the initial limitation of the alarm to the internal alarm horn 11 would not reduce the deterrent effect if an intruder has just entered the premises since the intruder will not be aware that only the internal alarm horn has sounded. In the event that the first trigger is longer than a predetermined period, say 10 seconds, as would be caused by cut wires, a broken window tape or the like, of zones Z4 or Z5 e activated, both alarm 11 12 will be activated.

In the event that tie alarm atem is .rmeciC to a telephone dialling device via socket 15, the micro-processor unit 7 activates the dial ler hold control voltage output to inhibit the dialler when only the internal alarm horn 11 -As been activated, In the event that both th~ inter1al ;.e external alarm horns 11 and 12 are AWrti vated, the dial ler w'11 be activated also. 't elated that the dialler hold function m messaye being transmitted to a remote pos ;e event that a false 870519, ltbspe.016,cadin.spe, -12 1 alarm occurs.

2 As an alternative to the above mode of operation, the 3 micro-processor unit 7 may be programmed such that the first 4 time any one of zones Z1 to Z5 triggers an alarm, both the internal and external alarm horns 11 and 12 are activated, 6 but any subsequent trigger from the first triggered zone 7 after the alarm horn has stopped sounding, only the internal 8 alarm horn 11 will be activated. It will be appreciated 9 that even if al l zones are triggered in a first intrusion, only the first to be triggered will lose the ability to 11 sound both the internal and external alarm horns during any oo 12 second intrusion. In this way, all zones have the abil ity a o 13 to sound both alarm horns at least once during repeated 0 o 14 initrusion attempts.

S' Referring now to Figure 2 of the drawings, a more 16 detailed circuit diagram of the block diagram of Figure 1 is 17 provided. Since much of the circuitry shown will be self- 18 explanatory to a person of skill in the art, only certain 19 parts of the circuitry will be described in greater detail.

20 The power supply circuitry 1 will be seen to comprise a O44 21 full wave bridge rectifier, the output from which is S 22 filtered and regulated by an LM317 three terminal regulator. a 41 oa 23 A current limiting transistor Qll is used to control the 24 current output of the LM317 to one amp. The back-up battery B is positioned to be float charged at al l times.

26 The shut-down circuit 5 will be seen to comprise a 27 voltage divider network R24, R24 to the mid point of which 28 is connected the positive terminal of a voltage comparator 29 U7. The negative terminal of the voltage comparator U7 is 870525, Itbspe.016,cadin.spe, L r~;l Irrl-- L-ili3ItX. 1 2 3 4 6 7 8 9 11 12 13 4 9 a 14 15 i I 16 17 18 19 21 22 i, 23 24 26 27 28 29 13 connected to a zener diode VR2 which provides a reference voltage of the order of 5.1V. The mid point of the voltage divider is normal ly at a voltage of 6.5V but in the event that the output from the back-up battery B falls below 5.1V, the output from the comparator U7 goes low thereby turning transistor Q10 off which in turn turns transistor Q4 off, shutting off the power supply to the voltage regulator 6 and deactivating the micro-processor unit 7.

The zone buffer/comparator 4 incorporates end of line resistors at the -emote ends of zones 1 to 5 and fire and provided that the voltage across these resistors is within the limits set by the comparators receiving the upper trip and lower trip reference voltages UT and LT, then circuit integrity is maintained. If the connection between the end of line resistors and the comparators is either opened or short circuited by an unauthorised person or by the detector, then an out of limit voltage will be detected by the comparators and an alarm condition will be registered.

The emergency input EMG is normally open circuit and is triggered by shorting it to ground or common.

The mode switching circuit 9 includes a main switch input MSI, a remote switch input RSI, a home switch input HSI and a radio signal or wireless input WI arranged as shown. The main switch input MSI is the main overriding input having control over the other switch inputs and being connected to the usual key switch on a front panel of the alarm system. In the open state, the alarm system is in the off mode and in the closed state, the alarm system is armed.

The remote switch input RSI provides the ability to include 870525, tbspe.016,cadin.spe, -14- 1 a remote control switch which is tamper proofed in the usual 2 manner. When the main key switch is turned on, the 3 terminating resistor of the remote sw'itch input circuit is 4 shorted out to fault the monitored open circuit input.

Similarly, if an intruder were to cut or short this input 6 line, the same result would be achieved. The remote switch 7 input to the micro-processor unit 7 is verified 5mS after 8 the initial response before accepting the changed input 9 state to ensure that the system will not return to an exit mode if the 'line from the remote switch is cut while the 11 alarm system is armed.

o 12 The home switch input HSI allows the alarm system to be 13 set such that a low volume entry tone will be sounded on the 14 internal alarm horn 11 for a predetermined period, for 0 15 example 30 seconds, before both the internal and external 0 16 alarm horns are activated at full volume. This allows the 17 user to deactivate the system in the event that the system 0 18 is inadvertently tripped.

19 The alarm signal generated by the micro-processor unit 20 7 for the internal and external alarm horns 11 and 12 21 comprise amplifier circuits 13 and 14 for producing the mute 22 signals and further amplifier circuits 15 and 16 for 23 producing the loud alarm horn signals. Each alarm horn 11 24 and 12 is also provided with a tamper circuit comprising a gating diode from each horn output connected to ground. If J 26 the horn wires are cut the tamper input will latch and 27 activate the alarm. A tamper switch is also associated with 28 the main control panel and operates in the usual manner.

29 With the exception of the special features described in 870519,ltbspe.016,cadin.spe, 1 greater detail above, the operation of the alarm system is 2 otherwise substantial ly standard. The alarm system includes 3 the usual LED display panel which indicates the status of 4 the system, includes a special alarm sound when the fire input is triggered and includes an emergency input which 6 overrides the other functions to sound both alarm horns at 7 full volume. The usual bypass switches are provided to 8 allow the system to be set up and tested by an installer or 9 service man. The control panel may include a mute button which holds the alarm horns 11 and 12 in the mute mode 11 during installation and testing or during an initial user o 12 familiarization period. The system may also be arranged to 13 render the alarm horns 11 and 12 inoperative where the 14 system is connected to a telephone dial ler.

O 15 Referring now to Figure 3, a telephone dial ler 016 inhibiting circuit embodying the invention is shown in block 17 diagram form. It will be appreciated that the circuitry 18 shown wil 1 be repeated for each of the N zones (usually S19 eight) of the alarm system to which the dial ler is to be 20 fitted. The circuitry shown may be supplied as an 21 accessory to be added to any alarm system having a dialler 22 or the circuitry may form part of the dial ler circuitry S 23 itself. In the latter case, the previously described 24 embodiment may be modified to exclude the inhibit on the dial ler input since this function would be performed by the 26 dia1 ler circuitry.

27 Referring to Figure 3 each zone input connects through 28 an unsealed zone lockout circuit 20 to prevent out of 29 service (or faulted) zones from interfering with the correct 870525, Itbspe.016,cadin.spe, crr~ a, o a a ao o 4

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16 operation of the system. During an off period and during the 90 second exit period a 90 second delay circuit 21 controls the lockout circuits 20 and the bypass switch circuit 22, allows the true state of each zone to be present at the dialler inputs so that true information about any zone can be interpreted during the testing of the complete alarm system including the dialler operation.

Switches 1 to N are provided to enable selection of acivation by a single or double trigger pulse input. A single trigger selection is used for one-shot input devices such as pressure mats, photo-electric beams, hold-up alarms and the like. All other detection devices usually product two or more trigger pulses and are set in position 2 when the switches 1 to N are in that position, a trigger from the alarm panel is received and is counted once by a divide by two counter 23 and starts a 10 minute reset delay circuit 24 and a 10 second presence enable circuit 25. The 10 minute reset delay circuit 24 resets the divider 23 Ecter minutes so that old stored information random one-shot triggers) that potentially could remain for days or weeks is deleted. A 10 second presence enable circuit discriminates against random one-shot triggers (usually less than 10 seconds) but looks for triggers that are longer than seconds. Such triggers will be caused by broken window tape, forced doors fitted with reed switches and cut wires.

Circuit 25 operates the bypass switch circuit 22 to bypass the divider 23. The output of divider 23 trips a 10 minute enable circuit 26 which unclamps (enables) all zone inputs to trigger their appropriate dialler inputs as applicable.

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b70525, Itbspe.016,cadin.spe, S17 1 Enable circuit 26 also operates bypass 22 which renders the 2 divider 23 ineffective for the 10 minute period. Thus any 3 activity, including one-shot events, are taken seriously and 4 allow all information to be passed to the dial ler.

It wi 1l be appreciated from the above that two random 6 one-shot events have to occur within a 10 minute period for 7 the dialler to operate and pass the information. Thus, the 8 prin iple of operation of this circuit is essentially 9 identical to that of the first embodiment described above.

The first embodiment described above may optionally be 11 fittod with remote satellite alarm horns and a particularly 12 preferred remote satellite alarm horn will now be described o. 13 with reference to Figures 4 and 5 of the drawings.

14 As indicated above, it is usual for an alarm system to S° 15 include an indoor and an outdoor alarm horn which is driven 16 by an electronic siren generator controlled by the alarm 17 system. This arrangement works well in most cases, but with o 18 increasing knowledge of alarm systems a trend is emerging 19 whereby some intruders wl 1 cut the wires to the alarm horn or smash the control box and with some systems either action 21 may result in the alarm system being rendered inoperative.

22 While satellite siren units which contain rechargeable 23 batteries and a siren generator in the same remote box a re 24 known to overcome this problem, a problem with such satellite sirens is that where a mains power failure occurs, 26 the back-up battery slowly discharges and the siren will be 27 activated at a specific voltage thereby creating a false 28 alarm. This problem is overcome by the satellite siren 29 shown in figures 4 and 5 of the drawings.

870525, Itbspe.016,cadin.spe, j 18 1 Referring Firstly to Figure 4, the block diagram of the 2 improved satellite siren will be seen to comprise a stand-by 3 battery which is trickle charged by a -voltage from the main 4 alarm system via the terminals SAT and -VE. The voltages also apply to tamper detection circuitry comprising a latch 6 1, a timer 2, a siren generating circuit 3 and 4 and 7 amplifier 5. Sudden removal of the voltage causes the latch 8 1 to trigger the timer 2 which in turn activates the siren 9 circuitry 3 to drive the horn speaker via the amplifier circuit 11 In the event that the main power supply is disconnected S12 either due to intentional disconnection or power failure the o 13 voltage of the remote battery will drop slowly. However, 14 since this voltage is applied to the latch 1 via an RC 15 coupled input, the time constant of which is very short (of 16 the order of lOOmS), the slowly dropping voltage input will 17 not trigger the latch thereby avoiding the creation of a o 18 false alarm.

19 VR1 provides a stable voltage pedestal of 8.2 volts, above which voltage electrical noise on the line wil 1 not 21 falsely trigger the siren.

22 Another mode of operation in lieu of switching off the i 23 SAT input to trigger the siren is to directly connect the 24 speaker output from the alarm panel to the S+ (speaker positive) terminal on the satellite module. This signal is 26 then amplified by the amplifier 5. The advantage of this 27 mode is that the satellite siren noise will be exactly the 28 same as the indoor siren generated by the alarm panel, that 29 is, synchronized.

870525, tbspe.016,cadin.spe, i 19 4 1 2 3 4 6 7 8 9 11 12 0 0v o or :3 13 04 00 0 0 g 15 09 B0 16 17 18 19 21 22 23 24 2E 26 27 Another feature is provided by clip/mixer 4. This allows low level tones from the alarm panel (as used for radio control alarm on/off confirmation) to sound at their originally intended volume through the satellite horn speaker without amplification, provided the level is below 3 volts.

If desired, a strobe light may be provided to serve as an additional warning to a returning occupant that an alarm has occurred. The strobe operation is exactly the same a., the siren but requires an extra wire connected from the alarm panel to the STR (strobe output) terminal. The duration of time the strobe operates for is controlled by the alarm panel, un less the wiring is cut, in which case the minute siren timer will control the strobe operating time. Switch 6 provides the bulk of the current to the strobe when driven by the STR input from the alarm panel.

By using a tamper switch within the satellite box connected back to the alarm panel, additional security is gained if the wires are cut, this is because the indoor speakers (driven by the alarm panel) and dialler if used, are triggered, thus giving maximum deterent effect.

The entire contents of the provisional specifications lodged with Australian Patent Applications of which this is the complete specification are hereby imported into this specification and form part of the disclosure of this specification. The claims form part of the disclosure of this specification.

870525, Itbspe.016,cadin.spe, I -L

Claims (13)

1. An alarm system comprising: a plurality of sensors each having means for providing a detection input signal adapted to cause activation of the alarm system; means for receiving a first detection input signal from any of said sensors; means for inhibiting activation of said alarm system when a a said receiving means receives said first detection input signal; 0 C' a1Q- and and o means for removing said inhibition and allowing activation o of said alarm system when said receiving means receives a second a o n detection input signal from any one of said plurality of sensors at any time within a predetermined time of said first detection input signal. o

2. The alarm system of claim 1, further including a first alarm device located essentially indoors on the premises to be 0 protected, a second alarm device located outdoors on the premises to be protected, said inhibition means allowing activation of said first alarm device only, said second alarm device being activated if a further detection input signal is received within jD said predetermined time.

3. The alarm system of claim 1, including naans adapted to transmit an alarm signal to a remote location, said transmitting means being inhibited when said first detection input is received and being activated when a further detection input signal is received indicating that a false alarm has not occured. tbspe.048/cadin. la 90 7 6 A o/^s L y/ 21

4. The alarm system of any preceding claim, wherein said predetermined time is of the order of five or ten minutes.

The alarm system of any preceding claim, including circuit means for activating the alarm system in the event that said first detection input is of a duration greater than about five to ten seconds or in the event that said first detection input is from a one-shot detection device.

6. The alarm system of any preceding claim, further including alarm horns and a selectable mute circuit which operates to Co 0i- reduce the voltage applied to the alarm horns and therefore the o 0 output from the horns for testing and for an initial 6 familiarization period.

7. The system of claim 6, further comprising a selectable home mode circuit in which the alarm system is activated in the mute 0 0, mode for an initial period of the order of thirty seconds. 0 00 0

8. The alarm system of any preceding claim, further comprising a satellite alarm unit including an alarm means, a main power supply, a remote power supply, a power supply circuit for supplying power to said alarm means from either said main power 9 supply or said remote power supply, and circuitry for detecting disconnection of or tampering with said unit, and circuit means for detecting an abrupt change in the voltage supplied by the main power supply to cause the alarm to be activated but which prevents activation of the alarm in the event that the voltage drops slowly, as would occur in the case of discharge of the remote power supply.

9. The alarm system of any precedi:', claim comprising: tbspe.048/cadincla 90 7 6 \iA 4 I 0 i/ A 1 X 4 A -22 alarm circuitry requiring a minimum predetermined voltage for proper functioning; a back-up power supply having a voltage; and a shut-down circuit responsive to the voltage of the back-up power supply dropping below said predetermined voltage to deactivate the alarm system.

The alarm system of claim 9, wherein said shut-down circuit includes a voltage comparator which compares a reference voltage with the voltage at the mid point of a voltage divider connected l9, across the back-up power supply.

11. The alarm system of any prGceding claim, including at least I two alarm devices having cyclic outputs which are out of phase by a predetermined amount.

12. The alarm system of claim 11, wherein said outputs are 180' 0 out of phase. 00

13.The alarm system substantially as hereinbefore described with o a reference to the accompanying drawings. o o DATED this July 6, 1990 SMITH SHELSTON BEADLE Fellows Institute of Patent Attorneys of Australia i Patent Attorneys for the Applicant: CADIN ELECTRONICS PTY. LTD. tbspe.048/cadin.cla 90 7 6 e i S'