WO1979000844A1 - Dispositif pour systeme de securite - Google Patents

Dispositif pour systeme de securite Download PDF

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Publication number
WO1979000844A1
WO1979000844A1 PCT/SE1979/000068 SE7900068W WO7900844A1 WO 1979000844 A1 WO1979000844 A1 WO 1979000844A1 SE 7900068 W SE7900068 W SE 7900068W WO 7900844 A1 WO7900844 A1 WO 7900844A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
answering
interrogation
unit
transmitter
Prior art date
Application number
PCT/SE1979/000068
Other languages
English (en)
Inventor
R Svensson
Original Assignee
Saab Scania Ab
R Svensson
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Saab Scania Ab, R Svensson filed Critical Saab Scania Ab
Publication of WO1979000844A1 publication Critical patent/WO1979000844A1/fr

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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/02—Monitoring continuously signalling or alarm systems
    • G08B29/06—Monitoring of the line circuits, e.g. signalling of line faults
    • G08B29/08—Signalling of tampering with the line circuit
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B26/00—Alarm systems in which substations are interrogated in succession by a central station
    • G08B26/006—Alarm systems in which substations are interrogated in succession by a central station with substations connected to an individual line, e.g. star configuration

Definitions

  • the present invention relates to an arrangement for security systems for status reporting from detectors set up in a protected location to a monitoring centre, and monitoring of the operational condition of communication lines which are arranged to connect the detectors to the monitoring centre.
  • an interrogation unit is pro ⁇ vided for each detector, and an answering unit is arranged in each detector.
  • Each interrogation unit is connected via a communication line to an answering unit co-acting with it.
  • the interrogation unit comprises an interrogation signal transmitter and an answering signal receiver, and the answering unit has an interrogation signal receiver and an answering signal transmitter.
  • the transmitter of the interro ⁇ gation unit is arranged to produce and send an interrogation signal to the answering unit, and the latter is arranged to receive the interro- gation signal and to produce and send back an answering signal to the interrogation unit, depending on the interrogation signal.
  • the answering unit is arranged to recognise this and to produce and send back to the monitoring centre an alarm/sabotage signal which is different from the answering signal associated with the interrogation signal.
  • the interrogation unit is arranged to receive answering signals and alarm/sabotage signals respectively, and to identify them.
  • OMPI unit by means of a function which is separate from the communication line checking arrangement, in that the answering unit transmits to the interrogation unit an alarm/sabotage signal consisting of a constant tone with a third specific frequency F3.
  • the arrangement in the said Patent sends pulses with different time intervals and with a constant frequency content between the int rogation and answering units, it is relatively easy for an unauthori sed person to manipulate the equipment so as to prevent the indicati of alarm status when a break-in into the protected area is imminent. All that is required to simulate that the line is whole and to preven an alarm signal from being sent to the monitoring unit is for the answering signal frequency to be listened to and for an answering signal producing device to be made which, on receiving an interroga ⁇ tion signal, produces a false answering signal, and which can be con nected in the communication line between the interrogation unit and the answering unit during the time interval between interrogation signals, at the same time as the communication line is broken beyond the answering signal producing device.
  • One object of the present invention is to remedy the said disadvanta by providing an arrangement of the type described in the introductio which, by continuous monitoring, prevents or makes very difficult an unauthorised manipulation with a view to misleading the monitoring centre in order to prevent the discovery of a projected break-in.
  • Another object of the invention is to provide a functionally-reliabl arrangement of the above-mentioned kind with which both communicatio line monitoring and status reporting from the detectors is effected simultaneously with the aid of the same functional units, by integra ted communication.
  • the interrogation signal produced by the interrogation unit transmitter is information-bearing and is sent continuously;
  • a ran ⁇ dom number generator is connected to the transmitter and is arranged to vary the said information content stochastically;
  • the answering unit has a signal converter connected in between its receiver and its transmitter which is arranged to be influenced by the different status conditions prevailing at the detector and to endow the answering sig ⁇ nals with an information content which, in addition to the informa ⁇ tion content of the interrogation signal at the time, is also depen ⁇ dent on the actual status of the detector, and to send this answering signal continuously;
  • the interrogation unit comprises a signal conver ⁇ ter which is connected to the transmitter and is arranged to convert the transmitted interrogation signal to a reference signal, the infor ⁇ mation content of which is in a specific relationship to the instan ⁇ taneous information content of the transmitted interrogation signal;
  • a signal comparator is connected to the receiver and the
  • Figure 1 shows fundamentally a security system arranged according to the invention, in which the three detectors in a protected area are connected to a monitoring centre.
  • Figure 2 illustrates fundamentally in more detail the various functiono ⁇ nal blocks of the arrangement according to the invention and their connection with each other.
  • one large block C designates a monitoring centre and the other large block P designate a protected local located peripherally realtive to the monitoring centre.
  • the local is protected by three detectors D1, D2 and D3 respectively.
  • the monitoring centre has an interrogation unit 1 for each detector.
  • Each detector has an answering unit 2 and an alarm contact 2a and a sabotage contact 2s, these detector contacts being arranged to break when there is alarm or sabotage status.
  • the con ⁇ tacts of the detector are connected by lines 7 and 8 respectively to the answering unit.
  • Each answering unit is connected to a communica ⁇ tion line 3 for double-direction communication with its interrogatio unit.
  • the interrogation unit has a interrogation signal transmitter 9 which is connected to the communi cation line 3, a random number generator 10 which is connected to th interrogation signal transmitter 9, an answering signal receiver 12 which is connected to the communication line, a signal comparator 13 connected to the transmitter, and a signal converter 11 connected in between the transmitter and the signal comparator.
  • the answering unit comprises an interrogation signal receiver 4 connected to the communication line 3, an answering signa transmitter 6 connected to the communication line, and a signal con ⁇ verter 5 connected in between the receiver and the transmitter.
  • the lines 7, 8 of the contacts 2a, 2s are connected to the signal conver ter.
  • the first alternative arrangement is imagined to operate with a direct current signal which is transmitted continuously from the interrogation unit as an interrogation signal, and an alternating current signal with variable frequency which is transmitted continuo ly from the answering unit as an answering signal.
  • the answering uni 2 in this case is a so-called voltage-controlled oscillator (VC0) which has two separate control inputs, represented on the Drawing by an interrogation signal receiving and amplifying block 4 and the sig ⁇ nal converting block 5 connected thereto, and a signal output shown as an answering signal transmitting block 6 connected to the signal converting block.
  • V0 voltage-controlled oscillator
  • the signal converting block 5 receives status signals a or s from the contacts 2a or 2s respectively, for alarm or sabotage respectively.
  • the interrogation signal transmitter 9 of the interrogation unit has a number of different load resistances which can be connected indivi ⁇ dually by means of analogue gates.
  • the random number generator 10 is arranged to control the analogue gates of the transmitter so that load resistances are connected continuously, following on after one another without any time interval between them and varying in a random manner (stochastically).
  • the signal converter 11 consists of a voltage-con ⁇ trolled oscillator of the same type as in the answering unit.
  • the answering signal receiver 12 consists of an input amplifier of a con- v ⁇ ntional type.
  • the signal comparator 13 comprises the units, a binary computer, a short-term memory (latch), and a de-coder.
  • the interrogation signal transmitter 9 of the interrogation unit 1 loads the interroga- tion signal receiver 4 of the answering unit 2 and its own signal converter 11 with the load resistances which are varying stochasti ⁇ cally in time, whereupon the interrogation signal F is produced.
  • the interrogation signal receiver of the answering unit receives the interrogation signal F which is supplied to the signal converter 5. If no status signal a, s is coming from the detector contacts 2a, 2s via lines 7 and 8 to the signal converter, the interrogation signal F is converted to an answering signal Sf, which is the answering signal expected from the answering unit by the interrogation unit for the status "all in order", i.e.
  • the sig ⁇ nal converter 5 converts the interrogation signal F to an alarm answe ⁇ ring signal Sa, the frequency of which differs from that expected of the answering signal Sf.
  • the signal converter in this case converts the interroga ⁇ tion signal to a sabotage answering signal Ss, the frequency of whic differs in another predetermined way from that expected of the answe ring signal Sf and the alarm answering signal Sa.
  • the alternative answering signals Sf, Sa, Ss are transmitted by the answering signal transmitter 6 via the communication line to the interrogation unit answering signal receiver 12, and after amplification in the latter are supplied to the signal comparator 13.
  • a reference signal Sr is also supplied to the signal comparator, this reference signal having an informatio content which is in a specific relationship to that expected of the answering signal Sf.
  • the reference signal is compared by the signal comparator with the three alternative answering signals Sf, Sa and S
  • the signal comparison is based on the concept that the period time f the reference signal Sr is selected greater by a specific factor tha the period time for the answering signals Sf, Sa and Ss from the answering unit. In this way, the period time of the reference signal Sr can determine the time interval during which a period calculation of the answering signals Sf, Sa and Ss is carried out.
  • the calculated period number is trans ⁇ mitted to the short-term memory and alarm A or sabotage S respective are indicated for the answering signals Sa or Ss respectively, the calculated period number of these differing from the calculated peri number of the answering signal Sf.
  • the interrogation signal transmitter 9 of the interro ⁇ gation unit 1 consists of a so-called touch-tone generator which in this case has eight binary control signal inputs, and is arranged to transmit the interrogation signal F continuously, depending on the signals at the control inputs corresponding to a binary code, said interrogation signal F being a combination of, for example, two of eight selected frequencies.
  • the random number generator 10 is arranged to control stochastically the binary signal inputs so that a connec ⁇ tion varying in time in a random manner is obtained without pause for two out of the eight frequencies.
  • the signal converter 11 of the interrogation unit is arranged to convert in a predetermined way a certain chosen binary code to another such code.
  • the answering signal receiver 12 of the interrogation unit comprises a detector and a decoder which is arranged to convert incoming alternating current signals to a binary code.
  • the signal comparator 13 is arranged to compare two binary codes.
  • the interrogation signal receiver 4 of the answering unit is construc ⁇ ted in the same way as the answering signal receiver 12 of the interro- gation unit.
  • the signal converter 5 is of the same type as that of the interrogation unit, but has here in addition the two signal inputs for status signals a and s. The conversion by the signal converter of the incoming bynary code to another binary code is arranged to occur dependent on the said status signals.
  • the answering signal transmitter 6 is of the same kind as the interrogation signal transmitter 9 of the interrogation unit.
  • the interrogation signal transmitter of the interrogation unit sends out the interroga- tion signal F which is detected by the answering unit interrogation signal receiver 4 as a binary code.
  • the binary code is converted in the signal converter 5 depending on the possible status signals a, s and the code obtained controls the transmission by the
  • the answering signal is detected by the answering signal receiver 12 of the interrogation unit as a binary code.
  • the binary code corresponding to the interrogation signal F is converted by the signal converter 11 to a reference code, this reference code being in a specific relationship to the answering signal code of the answering signal Sf expected when the status "all in order" prevails at the de ⁇ tector.
  • the reference code is compared in the signal comparator with the three alternative answering signal codes and the signal comparato indicates alarm A or sabotage 5 for the codes corresponding to the answering signals Sa and Ss, which differ in a specific way from the reference code.
  • An unauthorised manipulation of the communication line 3 causes dis- turbances in the transmission of information, which are indicated by the signal comparator with the signal K, as a fault on the communica ⁇ tion line.
  • the third alternative arrangement is imagined to operate with direct current signals.
  • the interrogation signal transmitter 9 of the inter ⁇ rogation unit 1 and the random number generator 10 are of the same kind as in the first alternative arrangement.
  • the answering unit 2 is a direct current amplifier with two separate control inputs, shown as an interrogation signal receiver 4 and the signal converter 5 with a signal output represented by the answering signal transmitter 6.
  • the signal converter 5 and the answering signal transmitter 6 are arranged to convert in a predetermined way the interrogation signal F received by the interrogation signal receiver to a direct current answering signal, the magnitude Sf, Sa, Ss of which depends on the status "all in order" at the detector, or the alternative status signals alarm a and sabotage s respectively.
  • the answering signal receiver 6 of the interrogation unit is a con ⁇ ventional input amplifier.
  • the signal converter 11 is an amplifier which converts the interrogation signal received from the interroga ⁇ tion signal transmitter to a reference signal Sr, the magnitude of
  • the magnitude of the reference signal Sr is compared with the magnitudes of the three alternative answering signals Sf, Sa, Ss.
  • the signal comparator is designed to indicate alarm A or sabotage S for the signal magnitudes corresponding to the signals Sa and Ss.
  • An unauthorised manipulation of the communication line 3 influences the direct current signal coming into the interrogation unit so that it becomes less, or alternatively greater, than the three alternative answering signals Sf, Sa, Ss, and this is indicated by the signal comparator with the signal K, as a fault on the communication line.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Burglar Alarm Systems (AREA)

Abstract

Dans un systeme de securite, des detecteurs (D1, D2, D3) montes dans un local protege (P) informent un centre de surveillance (C) sur l'etat des lieux, controlent l'etat de fonctionnement des lignes de communication (3) qui etablissent la connexion entre les detecteurs et le centre de surveillance, et une unite d'interrogation (1) placee dans le centre de surveillance produit et transmet un signal d'interrogation (F) a une unite de reponse (2) connectee a l'unite d'interrogation et situee dans le detecteur. L'unite de reponse repond en produisant et en renvoyant a l'unite d'interrogation un signal de reponse (Sf) qui depend du signal d'interrogation. Lorsqu'un etat alarme/sabotage est indique par le detecteur, l'unite de reponse le reconnait et envoie un signal alarme/sabotage (sa/Ss) a l'unite d'interrogation, different du signal de reponse (Sf) dependant du signal d'interrogation. De maniere a empecher ou a rendre extremement difficile une manipulation non autorisee du systeme de securite ayant pour objet de tromper le centre de surveillance, et de maniere a obtenir un dispositif d'un fonctionnement sur dans lequel le controle des lignes de communication (3) et l'information sur l'etat des lieux provenant des detecteur (D1, D2, D3) s'effectuent simultanement au moyen des memes unites fonctionnelles par communication integree, le signal d'interrogation (F) transmis par l'unite d'interrogation (1) est transmis de maniere continue et avec variation stochastique de l'information contenue. L'unite de reponse (2) est concue pour doter le signal de reponse d'un contenu d'informations qui, en plus de l'information instantanee du signal d'interrogation, depend aussi de l'etat actuel (a, s) du detecteur, et pour renvoyer le signal de reponse de maniere continue.
PCT/SE1979/000068 1978-03-28 1979-03-28 Dispositif pour systeme de securite WO1979000844A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE7803437A SE7803437L (sv) 1978-03-28 1978-03-28 Forfarande for att vid en anleggning vars enheter er sammanbundna medelst en kommunikationsledning for informationsberande signaler, kontinuerligt overvaka tillstandet for de till kommunikationsledningen anslutna ...
SE7803437 1978-03-28

Publications (1)

Publication Number Publication Date
WO1979000844A1 true WO1979000844A1 (fr) 1979-11-01

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ID=20334417

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1979/000068 WO1979000844A1 (fr) 1978-03-28 1979-03-28 Dispositif pour systeme de securite

Country Status (2)

Country Link
SE (1) SE7803437L (fr)
WO (1) WO1979000844A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2651938A1 (fr) * 1989-09-12 1991-03-15 Santerne Sa Procede de surveillance de l'etat d'au moins un moyen de detection, moyens en vue de la mise en óoeuvre de ce procede et installation de surveillance pourvue de ces moyens.
EP0547458A1 (fr) * 1991-12-12 1993-06-23 Schaaf, Norbert Système radio d'alarme
WO2009087169A1 (fr) * 2008-01-10 2009-07-16 Robert Bosch Gmbh Dispositif de contrôle pour un système d'alarme, système d'alarme et procédé de contrôle du système d'alarme

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE329358B (fr) * 1970-01-08 1970-10-05 Ericsson Telefon Ab L M
US4044351A (en) * 1974-06-24 1977-08-23 Walter Kidde & Company, Inc. System monitor with innate line security ability
US4070669A (en) * 1975-09-15 1978-01-24 Gautier Gerard A Anti-fraud alarm transmission line security system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE329358B (fr) * 1970-01-08 1970-10-05 Ericsson Telefon Ab L M
US4044351A (en) * 1974-06-24 1977-08-23 Walter Kidde & Company, Inc. System monitor with innate line security ability
US4070669A (en) * 1975-09-15 1978-01-24 Gautier Gerard A Anti-fraud alarm transmission line security system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2651938A1 (fr) * 1989-09-12 1991-03-15 Santerne Sa Procede de surveillance de l'etat d'au moins un moyen de detection, moyens en vue de la mise en óoeuvre de ce procede et installation de surveillance pourvue de ces moyens.
EP0547458A1 (fr) * 1991-12-12 1993-06-23 Schaaf, Norbert Système radio d'alarme
WO2009087169A1 (fr) * 2008-01-10 2009-07-16 Robert Bosch Gmbh Dispositif de contrôle pour un système d'alarme, système d'alarme et procédé de contrôle du système d'alarme

Also Published As

Publication number Publication date
SE7803437L (sv) 1979-09-29

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