WO1995030297A2 - Unite de securite empechant le piratage de lignes telephoniques - Google Patents

Unite de securite empechant le piratage de lignes telephoniques Download PDF

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Publication number
WO1995030297A2
WO1995030297A2 PCT/DK1995/000173 DK9500173W WO9530297A2 WO 1995030297 A2 WO1995030297 A2 WO 1995030297A2 DK 9500173 W DK9500173 W DK 9500173W WO 9530297 A2 WO9530297 A2 WO 9530297A2
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WO
WIPO (PCT)
Prior art keywords
code
line
telephone
telephone line
unit
Prior art date
Application number
PCT/DK1995/000173
Other languages
English (en)
Other versions
WO1995030297A3 (fr
Inventor
Christian Henri Krause
Original Assignee
Christian Henri Krause
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 Christian Henri Krause filed Critical Christian Henri Krause
Priority to AU24448/95A priority Critical patent/AU2444895A/en
Priority to EP95918539A priority patent/EP0759244A1/fr
Publication of WO1995030297A2 publication Critical patent/WO1995030297A2/fr
Publication of WO1995030297A3 publication Critical patent/WO1995030297A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/66—Substation equipment, e.g. for use by subscribers with means for preventing unauthorised or fraudulent calling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/66—Substation equipment, e.g. for use by subscribers with means for preventing unauthorised or fraudulent calling
    • H04M1/667—Preventing unauthorised calls from a telephone set
    • H04M1/67—Preventing unauthorised calls from a telephone set by electronic means
    • H04M1/673—Preventing unauthorised calls from a telephone set by electronic means the user being required to key in a code

Definitions

  • the present invention relates to a security unit for a telephone system which makes it possible to distinguish between authorised and unauthorised use of a telephone line. According to a further embodiment, the invention relates to a security unit which automatically implements measures to prevent unauthorised use of a telephone line.
  • Telephone lines are available in out-of-doors junction boxes and telephone cabinets which are to be so designed that they are easily opened by any service engineer which also makes them easy to open for intruders.
  • the telephone cords in the telephone cabinets are functionally exactly like the ones of normal telephone installations, i.e.
  • FR patent application No. 2 655 224 discloses a device for protecting a subscriber's communication line against unaut ⁇ horised parallel use.
  • This disclosure describes a unit which surveys the voltage on the telephone line whereby it is detectable whether an apparatus is coupled to that telephone line where the phone handle is lifted off.
  • the unit is intended for insertion into the telephone line before the authorised apparatus and constructed to be able to measure the current which runs in the line. If a current is detected in the line it means that the apparatus used is the authori ⁇ sed one. If, on the other hand, the presence of an apparatus with the handle lifted is detected by the current measurement without simultaneous detection of a current, this means that the apparatus in question is coupled in between the exchange and the security unit, i.e.
  • the security unit reacts to this by drawing a loading current which reduces the voltage on the telephone line to a level which is too low for the exchange to detect number signals from a dialling apparatus.
  • This known unit maintains a certain residual voltage in the line which is necessary to maintain the voltage supply and the functioning of the apparatus.
  • the residual voltage is high enough for an apparatus with a sound signal device to function and communicate.
  • 0 126 496 discloses an electronic lock for a subscriber's telephone line which comprises a circuit to be coupled in to load the telephone line and a code receiver unit which may detect whether a predetermined code is emitted onto the line and which may act on the right code by disconnecting the load.
  • the subscriber to use the telephone apparatus therefore needs to emit the code by means of the numerical generator of the apparatus which is a troublesome and unwanted procedure.
  • the load prevents calls with dialling telephones.
  • a telephone apparatus with a sound signal device may readily be used without the known device being able to prevent it.
  • a security unit comprising a coupling to an incoming telephone line and a coupling to an outgoing telephone line, a current threshold comparator designed to detect the current in the telephone line and determine whether the numerical value of the current I in the telephone line exceeds a determined threshold value I ⁇ and to emit a corresponding logical signal, a code memory so constructed that any code can be stored and transmitted, a code modulator arranged for dialling a code signal on the incoming connection under the control of a logical unit, and a microprocessor arranged for functioning by power supply from the incoming telephone line and in such a manner that it can receive signals from the current threshold comparator and the code memory and emit control signals to the all-or nothing relay and the code modulator, the microprocessor being programmed to react to a signal from the current threshold comparator indicating that the threshold value has been exceeded by emission of the code from the code memory through the code modulator, following which it becomes passive, in which state it does not react again until the comparator has indicated that the threshold value has not been
  • a very convenient security unit which operates automatically to emit a pre-programmed code which indicates that the relevant use is authorised without any inconvenience being experienced by the user of the telephone.
  • the only thing experienced by the user is a short delay, e.g. of less than one second, before the line is open, and follo ⁇ wing opening of the line the telephone is experienced as operating as usual.
  • the security unit comprises a particular number emitter, this number emitter may easily be arranged to transmit the code signal in a manner which will not be detected as a dialling number by the telephone exchange. Realization of the unit according to the invention is furthermore easy since it does not require any other energy supply that the one obtained through the telephone line. It is suitable for integration into a telephone apparatus or a telephone outlet.
  • the user's apparatus is disconnected while the code is emitted thereby avoiding any inconvenience to the user caused by code signals.
  • the unit is so arranged that, during the period when it maintains the user's telepho ⁇ ne apparatus disconnected, it draws a current of such magnitude that the telephone exchange will detect that the telephone line from the subscriber's apparatus is constantly connected and in the state "handle lifted off” .
  • the exchange is not disturbed by the disconnec ⁇ ting procedure, including that its debitor counter will not register it as a new call.
  • a chief security unit which, compared to the ordinary security unit, further comprises a current threshold comparater arranged to detect the voltage U across conducter pair in the telephone line and to determine whether the numerical value of the voltage drops below a determined threshold value U ⁇ and to emit a corresponding logical signal, and a code demodulator arranged to detect and decode a signal emitted from a code modulator in a security unit coupled to the same telephone line, said microprocessor being further arranged to receive the signals from the current threshold comparator and the code demodulator and to emit an output signal, said micropro ⁇ cessor being programmed to react to a signal from the current threshold comparator indicating that the threshold value is below the threshold by checking (a) whether the current threshold comparator indicates that exceeding has taken place, and (b) whether it receives through the code demodula ⁇ tor a code signal which corresponds to the code stored in the code memory, and in the instance that just one one of the qu ⁇ estions (a) and (b) is responded in the affirm
  • a security unit which may be connected anywhere along the telephone line and which may communicate with any number of ordinary security units and which may continuously monitor the entire telephone line and react as soon as an unauthorised state occurs.
  • the unit comprises a short circuit relay whereby the telephone line is short circuited within e.g. one fraction of a second in case there is any sign of unauthorised use.
  • a short circuit relay whereby very efficient security against theft of telephone time is obtained with an apparatus which may be connected anywhere on a line, e.g. in a usual telephone outlet without the need for any sort of intervention into the fixed installation.
  • the system works through the exchange of a code or password which is programmed into the individual security units and which may be changed according to need thereby allowing the connections to be opened or closed as desired.
  • the system is active in case of both outgoing and incoming calls; thus it is not possible either to answer an incoming call through an unauthorised apparatus.
  • the unit is provided with a device for monitoring the voltage on the telephone line and to emit a particular signal in case the line voltage is disconnected due to external disturbances.
  • a device for monitoring the voltage on the telephone line and to emit a particular signal in case the line voltage is disconnected due to external disturbances.
  • the user is informed in case the apparatus has been disconnected or short-circuited for external reasons, e.g. in case an unauthorised person should have found out how to avoid the short-circuit in the chief security unit by interrupting this portion of the telephone line to make an unauthorised call.
  • the chief unit is constructed in the same way as the ordinary security unit, it being determined by simple switching whether it operates as a chief or as an ordinary security unit. Such switching may e.g. be realised by operating the functions of the chief security unit by means of a battery whereas, when no battery is inserted, the unit automatically switches to function as an ordinary security unit.
  • Fig. 1 is a flow chart depicting the security unit according to the invention
  • Fig. 2 is a more detailed diagrammatical view of the security unit according to the invention
  • Fig. 3 is a diagrammatical view of a telephone line with several apparatuses connected thereto, said apparatuses being provided with security units according to the invention.
  • fig. 1 is a flow chart of a security unit.
  • the security unit which is designated as a whole with the reference numeral 20, comprises a connector 15 for an incoming telephone line and a connector 16 for an outgoing telephone line. Between these connectors which are realised in the form of telephone outlets, supply terminals or the like, an electric communication in the form of the line 25 is established, thereby allowing the security unit to be inserted into an ordinary telephone line.
  • the telephone line which in fig.
  • 1 is shown in one-line-form, comprises a conductor pair extending from a telephone exchange or the like and to a telephone apparatus or the like installation so as to conduct electric current in the loop formed by the two conductors in the conductor pair and by the lines which are in the equipment of the exchange and the telephone apparatus, respectively, said equipment being constructed to generate and detect variations in the electric currents thereby allowing different signals to be transmitted in both direc ⁇ tions in the telephone line.
  • the line in the subscriber's apparatus In its resting state the line in the subscriber's apparatus is disconnected or substantially disconnected, and the exchange supplies the line with a constant voltage of a magnitude of 43-40 V, thereby making a certain electrical effect available to the telephone subscriber.
  • Some state of the art telephone sets draw a weak current, e.g. for maintai ⁇ ning an electronic memory or the like. This current is not considered to substantially exceed 1 mA.
  • circuits When the subscriber lifts the handle of his telephone set, circuits are connected which draw a current of constant or varying magnitude.
  • the current magnitude may vary e.g. depending on signals for the transmission of speach, digital information, number calls, etc.
  • the current magnitude is assumed to vary about approximately 35 mA, and the line voltage varies within the interval of 5-15 V.
  • the exchange In case of the "ringing" state, the exchange emits a ringing signal in the form of a voltage which varies between 0 and 110 V.
  • shut-down state is the state in which the power across the line is 0, e.g. because the line has been disconnected at the telephone exchange, the line has been interrupted, or the line has been short-cir ⁇ cuited. Irrespective of the causes, in this state of the line anybody who uses a connected apparatus will perceive the telephone line as completely dead.
  • the security unit 20 further comprises the following components:
  • a microprocessor 1 with a power supply inlet 1, an analogous entry port 7, digital entry ports 8 and 13 through 22 and digital exit ports 6, 9, 12, and 23 through 27.
  • a battery 17 which may supply power to the microproces ⁇ sor 1 at its inlet 1 through a rectifier.
  • a code modulator 18 connected to the line 25 and having a connection to the logical exit port 6 of the micro- processor so as to permit the microprocessor to generate code signals through signals on its exit port, said signals being dialled onto the line 25. Moreover the code modulator 18 serves the purpose of trans ⁇ mitting electric power through a particular outlet connection which, through a rectifier, is connected to the microprocessor at its inlet 1, thereby allowing the microprocessor to receive electric current from the telephone line therethrough.
  • a code demodulator 19 connected to the line 25 and having a line to the logical entry port 7 of the micro ⁇ processor 1, through which the microprocessor may read code signals off the telephone line and detect whether there is current on the line.
  • a current threshold comparator 4 which is connected to the conductor pair 25 and which generates the numerical value of the voltage U on the conductor pair and compares it to a determined threshold value voltage U ⁇ .
  • the current threshold comparator 4 is connected to the battery 17 and operates actively only when supplied with power from the battery.
  • the current threshold comparator 4 emits an affirmative signal to the microprocessor 1 on its logical entry port 8 in case the numerical value of the line voltage has been found to be below the threshold value, presupposing, however, that battery voltage is present. In all other instances no affirmative signal is emitted.
  • a short circuit relay 5 is connected to short-circuit the conductors in the line 25 under the control of a signal from the microprocessor 1 on the logical exit port 9 thereof. Short-circuited position is designated the activated position, and interrupted position as deactivated position.
  • a current threshold comparator 6 as inserted on the line 25 generates the numerical value of the loop current I in the line 25 and compares the latter to a threshold current value I ⁇ . In case the result of such comparison is found to be positive an affirmative signal is emitted to the microprocessor at the logical entry port 13 thereof.
  • a disconnecting relay 7 inserted in the line 25 to allow it to interrupt the communication with that portion of the line 25 which leads to the connector 16 to the outgoing line.
  • the disconnecting relay is controlled by a signal from the logical exit port 12 of the microprocessor 1.
  • "Disconnected state” is designa ⁇ ted the activated state whereas the "shut down state” is designated the deactivated state.
  • An alarm signalling device 11 controlled by the microprocessor 1 through its logical exit port 25 and so devised as to emit a particular alarm signal, e.g. a visual or an acoustic signal.
  • An interruption indicator 13 which is controlled by the microprocessor 1 through its logical exit port 23 and constructed to provide a particular indication, e.g. a visual indication, in case a telephone line break-in has been detected.
  • a reset panel 14 which is connected to the logical entry port 22 of the microprocessor 1 and so arranged that upon activation of e.g. a spring loaded push button, a user may cancel the indications and acknow ⁇ ledge receipt thereof, respectively.
  • the security unit comprises a code memory 8 which may be read by the microprocessor 1 at the logical entry ports 14-21. A password or code number chosen by the user is stored in the code memory.
  • the security unit is so constructed that it may operate with or without the battery.
  • the microprocessor 1 obtains its power supply from the telephone line thorugh the particular line on the code modulator. As shown in fig. 1 a rectifier is inserted into the line and a second rectifier is inserted into the line from the battery to keep the two power supplies apart.
  • the current threshold comparator is receives its supplies directly from the battery by a line connected before the rectifier in the battery connector which means that the current threshold comparator is not supplied with power unless a battery is mounted in the unit.
  • a security unit without battery substantially acts as a code transmitter only whereas a security unit with battery acts as a code receiver and code approver and may activate alarms and short-circuit the telephone line according to certain criteria.
  • On one telephone line several telephone apparatuses may be mounted which are each connected thereto through each their security unit.
  • One of the security units is provided with battery and thus acts as chief security unit in the system.
  • a security unit without battery serves as ordinary security unit.
  • the current threshold comparator 6 ensures that current is drawn in the line, and an impulse is trans ⁇ mitted to the microprocessor 1 on its entry port 13.
  • the microprocessor checks whether it has received a positive signal on the logical entry port 8. In the negative, it switches to a state where it draws current from the line through the code modulator 18 of a current magnitude of above 15 mA, following which it activates the relay 7 that dis ⁇ connects the line to the local telephone set and it reads the code stored in the code memory 8 and transmits the code number on the telephone line through the code modulator 18.
  • the disconnection of the local telephone apparatus by the disconnecting relay 7 serves the purpose of preventing that the transmission of the code number disturbs the user of the local apparatus.
  • the disconnecting relay is again switched to deactivated state, i.e. the state in which the telephone line is shut down and the local apparatus connected to the line.
  • the microprocessor 1 ceases to draw current through the code modulator and switches to a substantially passive state. Except from a very brief clicking sound, the user of the local telephone set will be persuaded that connection is not obtained until completion of the transmission. Since, however, the transmission may be carried out in less than one second, such additional waiting is considered acceptable.
  • the ordinary security unit does not fulfil any other functions, i.e. it does not monitor break-ins on the telephone line or interruptions and it does not transmit any alarm messages.
  • a security unit with battery serves as chief security unit.
  • the current threshold comparator 4 is constantly active and in case the voltage on the telephone line drops below the threshold value, it will transmit a positive signal to the microprocessor 1 on the entry port 8. This means that the handle is lifted off a telephone set which is in communica ⁇ tion with the telephone line.
  • the microprocessor simultaneously receives a signal on the entry port 13 from the current threshold comparator 6, it means that current is drawn in the local telephone set and the microprocessor 1 does not take further action.
  • the microprocessor does not receive a positive signal on the entry port 13 it means that the handle is lifted off another telephone set connected to the telephone line. In this case the microprocessor awaits a code signal. Any such code signal will be received through the code demodulator 19 connected to the microprocessor entry port 7 so as to allow deciphering of an incoming code signal and comparison by the microprocessor to the code stored in its code memory 8.
  • the microprocessor awaits the transmission of code signals. If there is any sign of code pulsations, it awaits the code message and deciphers it.
  • the microprocessor If the codes match it means that the telephone apparatus in question is authorised, and then the microprocessor will not take any further action. If the microprocessor cannot match with its own code or if, following the expiry of said short waiting period, the microprocessor ascertains that no code at all was transmitted on the line, it means that the relevant use of the telephone line is unauthorised and the micropro ⁇ cessor will then activate the short-circuit relay 5 through its exit port 9 to short-circuit the telephone line. The telephone line is then dead and useless. At the same time the microprocessor makes an indication on the break-in indicator 12 and optionally it sets off an alarm on the alarm unit 11. In case no code signal is received, the line is shut down so fast that the apparatus of the unauthorised user will not have the time to starts its dialling tone.
  • the microprocessor 1 comprises an integral time circuit and it uses it in such a manner that, following a certain waiting period, e.g. 10 sees, it deactivates the short-circuit relay to open the telephone line whereupon it checks the signal from the current threshold comparator 4. If the current threshold comparator still emits a positive signal it means that the unauthorised use still takes palce and it will then reactivate the short-circuit relay 5 and the line is dead again. If there is no positive signal from the current threshold comparator it means that the relevant use of the telephone line has ceased and the microprocessor 1 sub ⁇ sequently switches to its normal resting state.
  • a certain waiting period e.g. 10 sees
  • the microprocessor is further constructed for continuously monitoring whether there is voltage on the line. This is effected through the port 7 which is in communication with the code demodulator 19.
  • the code demodulator 19 is so constructed that, while there is voltage on the line, it continuously emits an off-set voltage in addition to the code signals, which voltage may be detected by the microprocessor on its entry port 7.
  • the absence of offset-voltage on the entry port 7 means that the telephone line has been interrupted or short-circuited.
  • the microprocessor being, of course, able to distinguish when when the lacking voltage is due to short-circuit through the short-circuit relay 5, it is programmed to react to the absence of voltage in all other instances by indicating line- interruption on the interruption indicator 13 optionally in combination with an alarm on the alarm unit 11.
  • the line unit 3 comprises the two functional blocks, the code modulator 18 and the code demodulator 19. The signal from the line is transmitted through a rectifier bridge connected to the modulator part and the demodulator part.
  • the demodulator part consists substantially of the voltage divider constituted of the resistances R 2 and R 9 and a Zener diode Z 3 which serves to protect the microprocessor 1 against hypervoltages.
  • the voltage divider converts the signals received to a level which allows them to be processed by the microprocessor.
  • the modulator part comprises the transistor P 1# the resistance R 12 and the Zener diode Z 4 .
  • the modulator signal from the microprocessor unit is introduced on the basis of the transistor whereas current may be drawn from the joining point between the one pole on the Zener diode and the emitter of the transistor. From this point current can be drawn to supply power to those portions of the microprocessor which are to operate when the unit operates without battery, and a controlled current may be drawn which translates itself as a load on the telephone line so that the telephone exhange will also perceive the line as loaded while the connection is disconnected in the disconnecting relay 7.
  • the current threshold comparator 4 comprises a rectifier bridge, a transistor which derives its emitter voltage from the battery, and a resistance network adapted to effect that the transistor saturates when the voltage on the telephone line drops below a level of 28 V.
  • the current threshold comparator 6 comprises a rectifier bridge, the transistor P 3 , the Zener diode Z-, two diodes D and D 2 and various resistances. Among these, resistances R 7 and R 8 are inserted serially into the conductors of the telephone line, and the circuit is substantially devised to react when the voltage above these resistances exceed a certain magnitude.
  • the offset of the emitter is offset at the Zener diode Z x thereby ensuring that the circuit reacts at a certain current value.
  • the circuit is tuned so as not to react to small currents, e.g. the currents drawn by certain electronic telephone apparatuses in their resting states to maintain electronic memories and the like. Conveniently the circuit is constructed to react when the current magnitude exceeds 15 mA whereby it is ensured that the circuit reacts upon connection of any normal telephone set.
  • the code memory 8 comprises a manually activatable dip-switch, i.e. a series of switches which may each manually be set between to positions, all the positions of the switches being digitally readable. It lies within the scope of the invention to realise the code memory in other ways in the form of fixed wirings which may conveniently be arranged in a plug-in connector or in the form of a purely electronic memory wherein the code is programmed electronically.
  • the microprocessor 1 comprises a control unit which may e.g. be realised in a suitable microcomputer or microcontroller and various peripheral components.
  • the transistor P B may be activated directly by a signal from the current comparator through the condensator C 3 whereby it will substantially open the power supply from the code modulator and to the micropro ⁇ cessor at its entry port 1.
  • the microcomputer will be able to maintain the transistor P s open by providing a signal on the exit port 27 which extends to the basis of the transistor P s .
  • the transistor may also ensure that a current load is maintained on the telephone line.
  • the transistor P 5 ensures that power will not run in the opposite direction due to the rectifier effect thereof corresponding to the one of the rectifiers shown in fig. 1.
  • Power from the battery 17 is conducted through the transistor P 4 which, on the one hand, has a rectifying effect correspon- ding to the second rectifier of those shown in fig. 1 and on the other enables the microcomputer to keep the connection open following power supply due to the impulse from the current threshold comparator by providing the exit port 26 with a signal.
  • the entry port 7 of the microcomputer is an analogous entrance which enables the microcomputer to measure voltage levels and to determine whether the signals detected are code signals, dialling impulses or constant voltages.
  • the alarm unit 11 comprises a loudspeaker while the break-in indicator 12 and the interruption indicator comprises suitable control lights.
  • the reset panel 14 comprises a push button. Further details, including types and values for components, will not be described in further detail as they are considered to be within the knowledge of the skilled person.
  • fig. 3 is a one-line diagram ⁇ matical illustration of a telephone line 24 connected to an exchange 23 and to four different telephone sets which are each designated with the reference numeral 22.
  • the telephone line comprises a number of parallel coupled telephone outlets 21 and each of the telephone sets are plugged into a telepho ⁇ ne outlet 21 through each their security unit 20 according to the invention.
  • One of the security units is provided with a battery 17 whereby it reacts as chief security unit which is capable of short-circuiting the telephone line and to set off alarms and indications.
  • the chief security unit 17,20 continuously monitors the telephone line and, as soon as the line is loaded by lifting of telephone handles or by connection of an unauthorised telephone apparatus, it reacts by checking whether the approved code is emitted and in the negative, by short- circuiting the telephone line.
  • the function is active for outgoing as well as incoming telephone calls, i.e. an unauthorised apparatus can neither dial nor respond to calls. Only telephone sets connected through a security unit with the same code number as the one stored in the chief unit are allowed to avail themselves of the telephone line.

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  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Signal Processing (AREA)
  • Telephonic Communication Services (AREA)
  • Alarm Systems (AREA)

Abstract

Unité de sécurité (20) empêchant le piratage de lignes téléphoniques et comportant un raccordement (15) pour une ligne téléphonique d'arrivée et un raccordement (16) pour une ligne téléphonique de départ, un comparateur de seuil de courant (6) conçu pour détecter le courant parcourant la ligne téléphonique et donc le décrochement du combiné d'un appareil téléphonique raccordé à l'unité de sécurité, une mémoire de codes (8) permettant l'enregistrement et l'émission d'un code éventuel, un modulateur de codes (18) conçu pour appliquer un signal codé à la ligne d'arrivée, et un microprocesseur (1). Une unité de sécurité principale comporte un démodulateur de codes (19) conçu pour recevoir les signaux codés et un microprocesseur programmé de manière à réagir à un signal provenant du comparateur de seuil de tension en déterminant si l'utilisation de la ligne téléphonique ainsi détectée est autorisée ou non par l'émission du code agréé. Au cas où l'utilisation ne serait pas autorisée, la ligne peut être coupée par un relais de court-circuit.
PCT/DK1995/000173 1994-05-02 1995-04-26 Unite de securite empechant le piratage de lignes telephoniques WO1995030297A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU24448/95A AU2444895A (en) 1994-05-02 1995-04-26 Telephone break-in security unit
EP95918539A EP0759244A1 (fr) 1994-05-02 1995-04-26 Unite de securite empechant le piratage de lignes telephoniques

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DK0496/94 1994-05-02
DK49694 1994-05-02
DK0119/95 1995-02-02
DK11995A DK11995A (da) 1994-05-02 1995-02-02 Sikringsenhed til telefonsystem

Publications (2)

Publication Number Publication Date
WO1995030297A2 true WO1995030297A2 (fr) 1995-11-09
WO1995030297A3 WO1995030297A3 (fr) 1995-12-07

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EP (1) EP0759244A1 (fr)
AU (1) AU2444895A (fr)
DK (1) DK11995A (fr)
WO (1) WO1995030297A2 (fr)

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WO1996029811A2 (fr) * 1995-03-17 1996-09-26 Philips Electronics N.V. Systeme de communication pour detecter un terminal intrus non autorise
WO1998023078A1 (fr) * 1996-11-22 1998-05-28 Rune Eritzland Procede et dispositifs permettant d'assurer la securite de lignes de telecommunications
FR2769448A1 (fr) * 1997-10-06 1999-04-09 Nicole Maschio Dispositif de filtrage de communications telephoniques
RU2761351C1 (ru) * 2021-03-30 2021-12-07 Федеральное государственное автономное образовательное учреждение высшего образования "Национальный исследовательский университет "Московский институт электронной техники" Устройство для защиты от несанкционированного прослушивания разговоров в помещении

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US2466627A (en) * 1944-08-14 1949-04-05 Watford Electric & Mfg Company Electromagnetic escapement mechanism

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US4852155A (en) * 1987-04-17 1989-07-25 Schlumberger Industries Systeme d'authentification analogique reciproque entre un terminal et une ligne de transmission
GB2205216A (en) * 1987-05-09 1988-11-30 Alcatel Nv Circuit arrangement for monitoring a telephone line
US4969178A (en) * 1989-10-26 1990-11-06 Telecommunication Laboratories, Directorate General of Telecommunications , Ministry of Communications Multipurpose subscriber local line monitoring device
FR2655224A1 (fr) * 1989-11-24 1991-05-31 Regnier Marc Dispositif de protection d'une ligne d'abonne contre un branchement illicite.
EP0454262A1 (fr) * 1990-04-26 1991-10-30 Koninklijke KPN N.V. Circuit électronique pour signaler et/ou empêcher l'usage abusif d'une ligne téléphonique d'abonné
EP0498734A1 (fr) * 1991-02-08 1992-08-12 France Telecom Dispositif pour la détection d'un branchement non autorisé sur une ligne téléphonique d'abonné

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996029811A2 (fr) * 1995-03-17 1996-09-26 Philips Electronics N.V. Systeme de communication pour detecter un terminal intrus non autorise
WO1996029811A3 (fr) * 1995-03-17 1997-01-03 Philips Electronics Nv Systeme de communication pour detecter un terminal intrus non autorise
WO1998023078A1 (fr) * 1996-11-22 1998-05-28 Rune Eritzland Procede et dispositifs permettant d'assurer la securite de lignes de telecommunications
FR2769448A1 (fr) * 1997-10-06 1999-04-09 Nicole Maschio Dispositif de filtrage de communications telephoniques
RU2761351C1 (ru) * 2021-03-30 2021-12-07 Федеральное государственное автономное образовательное учреждение высшего образования "Национальный исследовательский университет "Московский институт электронной техники" Устройство для защиты от несанкционированного прослушивания разговоров в помещении

Also Published As

Publication number Publication date
AU2444895A (en) 1995-11-29
DK11995A (da) 1995-11-03
WO1995030297A3 (fr) 1995-12-07
EP0759244A1 (fr) 1997-02-26

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