AN EMERGENCY CALL UNIT

Abstract: In the combination of a call unit (20) for an emergency call system with a remote trigger device (54), the call unit incorporates means for transmitting and receiving speech and/or data via the public switched telephone network (PSTN) in a hands-free mode. The remote trigger device (54), which may be a pendant (54) includes a keyboard (56) connected to a signal transmitter for remote operation of the transmitting and receiving means. The call unit includes a telephone line seizing system which comprises an actuating circuit and a seizing circuit. The actuating circuit comprises a resistor (82) for limiting current drawn from the PSTN, a switch (86) to make and break the actuating circuit and a darlington transistor (90) actuated by the actuating circuit to complete the seizing circuit and thereby seize the telephone line. The system will work to allow outgoing calls even if there is a mains electricity power cut.

Description: "AN EMERGENCY CALL DNIT" This invention relates to a call unit for an emergency call system such as used in sheltered housing schemes for the elderly and infirm and more recently in ordinary dwellings. Emergency calls system typically comprise at each dwelling to be monitored a call unit usually incorporating or for connection to a telephone and operable in a hands-free mode to transmit and receive speech and/or data via the public switched telephone network (PSTN). The call unit may also comprise an automatic dialler responsive to an alarm signal generated by an alarm button or by any of a wide variety of sensors or detectors commonly used with such systems. It is also common to provide a remote trigger device carried or worn by the occupier and in radio or other communication with the call unit. In the past, and in particular for use by the elderly or mentally disabled, the remote trigger device comprises a single alarm button. In accordance with one aspect of the present invention we propose in combination with a call unit in or for an emergency call system incorporating means for transmitting and receiving speech and/or data via the 3 dialling out to obtain help, it is known to provide a back-up battery to cover the situation where an emergency arises during a power cut so that the telephone unit is still able to seize the line of the public switch telephone network for the emergency telephone call to take place. A problem will arise however if the back-up battery is dead or runs out during a call. In addition, it may be inconvenient to have to provide a battery. According to another aspect of the invention there is provided a telephone line seizing system comprising an actuating circuit and a seizing circuit, the actuating circuit comprising means for limiting current drawn from the public switched telephone network (PSTN), first switch means to make and break the actuating circuit and second switch means actuated by the actuating circuit to complete the seizing circuit and thereby seize the telephone line. The telephone network providers specify that the current level drawn from the PSTN when the telephone is not engaged with a call must be below a low threshold. By means of the invention, however, the very low permitted current can still be used to enable the telephone line to be seized and no battery is required. Preferably means is provided for increasing the said ■ limited current supplied to the second switch means. Preferably, a rectifier is provided to rectify current from the PSTN. The means for limiting the current is preferably a resistor which may have a resistance of at least 2.2 kilohms. The means for increasing the limited current may take any suitable form and may comprise a darlington transistor. The second switch means may take any suitable form and may comprise a darlington transistor. Preferably a capacitor is provided before the first switch means to store energy to be used when the first switch means makes the actuating circuit to actuate the second switch means and thereby result in seizing of the telephone line. The system may be used to enable a telephone to be operated by a user or alternatively an autodialler may be provided arranged to be powered by the PSTN when the line has been seized. Preferably, means is provided to prevent repeated operation of the first switch means from interfering 5 with the autodialler. The means may take any suitable form and may comprise a diode capable of clamping the signal. Two embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 schematically illustrates an emergency call system of the first embodiment; Fig. 2 is a block diagram of the call unit of the emergency call system of Fig. 1; Fig. 3 schematically illustrates operation of the emergency control system of Fig. 1 in communication via the PSTN with a control centre; Fig. 4 schematically illustrates operation of the emergency control system of Fig. 1 in communication via the PSTN with an outside caller using a conventional telephone; and Fig. 5 schematically illustrates a circuit of the second embodiment. The emergency call system of Figure 1 to 4, includes a 6 call unit 20 connected to the public switched telephone network (PSTN) and having hands-free (loudspeaker) speech facility. The emergency call unit 20 includes a micro controller 24 and has a ringer 26, line switch 28, voice amplifier and switches 30, handset 32, microphone 34 and loudspeaker 36, -power supply 38, and a dialler 40 and tone encoder 42 as in a conventional hands-free telephone. The micro-controller 24 controls communication between the key-pad 44 and dialler 40, activates the line switch 28 and via the tone encoder 42 and tone decoder 46 establishes a two-way data link enabling interrogation of the micro controller 24 via an external telephone line and a speech encoder 48 outputs synthesised verbal messages composed of words and/or phrases pre-recorded in the micro controller, onto the external line. A ring detector 50 provides an input to the micro controller 24 to indicate receipt of an external call. When an alarm is raised for whatever reason, the system will dial out on the PSTN serving the premises in which the system is installed. In the case of sheltered housing schemes for the elderly, the controller may be connected directly, for example, by 7 dedicated lines, to a local warden or supervisor's office and capable of recognising the lack of response or an off-duty flag before dialling out on the PSTN to establish a telephone connection with a remote receiving station or control centre. In the illustrated embodiment, however, the system is designed to dial out up to three predetermined telephone numbers as a first priority. These may be the numbers of friends or relatives and the last may be a local warden or help centre. If all of these attempts fail, the system is programmed to dial the number of the remote receiving station or control centre. It will be understood, therefore, that the illustrated embodiment is not restricted to use in a sheltered housing scheme but may be used for monitoring any number of unrelated dwellings. Having established a connection with the control centre over the PSTN, the controller then transmits data identifying the (location of the) unit and the nature of the alarm depending upon how the emergency call was initiated. Most conventional emergency call systems include a portable alarm trigger in the form of a pendant or the like, carried or worn by the user (i.e. remote from the controller) and incorporating a radio, infra-red 8 or ultra-sonic transmitter operable in response to pressing of an alarm button to transmit signals to a receiver in the call unit controller for initiating the emergency call procedure. This procedure may also be initiated by other alarm triggers in the form of pull-cords fire detectors, low temperature detectors etc. In addition, any of a wide variety of activity detectors (e.g. point of entry sensors) are provided so that in normal use of the emergency call system an alarm can be raised if there has been insufficient activity over a given period. Such detectors also enable the system to provide intruder alarm protection. The micro-controller 24 is programmed to be set in intruder alarm protection mode using the same detectors as are used in the activity monitoring mode which is suspended when intruder protection is armed. A series of detectors D, to D N including the alarm trigger detectors and activity detectors, may all be hard wired to the emergency call unit but in this illustrated embodiment incorporate a radio transmitter in communication with a radio receiver 52 in the call unit. Associated with the call unit is a portable unit or pendant 54 having a key-pad 56 identical with the telephone key-pad 44 and in radio communication with the call unit 22 whereby all telephone key-pad functions can be performed remotely by a user either inside or outside (within a limited range) of the protected premises. The keypads have the keys; 1 ,2,3,4,5,6,7,8,9,0,*,#,A,B,C,MEM, LS,ALARM. An intruder alarm feature may be operated via the key pad on the fixed unit or on the pendant. To arm the intruder alarm the user enters a two-part key sequence. The first part identifies the function required, the second part assures security and comprises a Personal Identification Number (PIN) . For example, to arm the alarm the sequence might be #A019876. #A would select a special function, 01 would select which special function, i.e. arm alarm, and 9876 would be the PIN. Having successfully entered this sequence the system would be armed and activity monitoring suspended. An exit period of say 45 seconds is allowed if any of the sequence is entered via the fixed unit (telephone) keypad. To disarm the intruder alarm the user enters a 10 slightly different key sequence. For example, this might be #A029876 where #A selects a special function, 02 selects which special function, i.e. disarm alarm, and 9876 is the PIN. A 45 second entry period is allowed between the setting-off of an intruder sensor and the initiation of an alarm. During this period a disarm key sequence will cancel any intruder alarm and restore the emergency call unit to activity monitoring. This feature allows the fixed unit keypad to be used. The telephone facility is operable via either the fixed unit keypad 44 or the pendant keypad 56 in an identical manner. The pendant keypad 56 may be used if the user is remote from the fixed unit but within hearing distance of it. To initiate a telephone call from the pendant 54 the user first presses the key LS to instruct the fixed unit to seize the telephone line, after which the user is able to dial the desired telephone number in the normal way and the fixed unit would signal to the exchange. Having established a call, the user and called party are able to converse using the loudspeaking speech facility of the fixed unit. The user can drop the line by pressing the LS key again. Additionally, having seized the line, any of the fast 11 or abbreviated dialling facilities as also available on the fixed unit may be used. Another feature of the emergency call system, see particularly Figure 3, is the ability to send standard digital data to a control centre 60 which would be interpreted and acted on by the centre equipment and then supplementing that with verbal data messages which would be interpreted by the centre operator. With the system in an alarm state having been activated by the user or some automatic sensor, such as, for example, medical emergency, fire, intruder or heating plant failure, a telephone link with the centre equipment 60 is established. The system unit controller 22 then passes digital data to the centre 60 and expects to get some response to confirm a successful data transaction. This data includes the call unit identity and the type of alarm call. The choice of the latter is limited to the number of options available at the control centre 60. Control centres are normally computer based and the existence of the alarm call is indicated by a list of pending calls from which the control centre operator can choose. Having chosen the alarm call any data held in the computer relating to the particular system unit would be displayed. Some information displayed might 12 also relate to the alarm call type. A speech path is then established between the operator and system unit user under control of the operator precluding the transmission of further data. In the present system, however, pre-recorded verbal messages may be sent under command of the system unit controller, to elaborate on the type of call which initiated the alarm, by, for example announcing 'pullcord in bathroom' when the digital data only identifies a pullcord. In addition, verbal messages announcing further alarms such as 'fire 1 or 'intruder zone 1' might be generated providing the operator with a real time understanding of the activity at the system unit location. An alarm call is generated by the user, by for example activating the radio pendant 54 whose transmission is received by the radio receiver 52. The signal from the radio receiver 52 is sent to the microcontroller 24. The following sequence of activity of the call unit 22 is controlled by the microcontroller 24. The call unit 22 emits an audible bleep and flashes a lamp; at this stage the user may stop the alarm by pressing the cancel key on the key pad 44 or pendant key pad. After a period of 10 seconds the bleep stops and the lamp is illuminated constantly. This 13 signifies that the 'pre-alarm' period is over and the call unit will attempt to contact the centre and the user has no option to cancel. The call unit seizes the PSTN line by enabling the line switch 28 and dials the appropriate centre telephone number by activating the dialler 40. The call unit has a preset sequence of repeat numbers and different numbers to ring should it fail to establish connection to the central control receiving station on the first attempt. Having dialled the number the call unit outputs a 'cozy tone 1 from the tone encoder 46 onto the line. The 'cozy tone 1 serves two purposes: firstly it announces the fact that the equipment using the line is automatic dialling apparatus, should it inadvertently connect to the wrong party, and secondly it acts as an identifier to the central control receiving station so that it is recognised as alarm equipment. When the central control receiving station detects ringing on one of its lines it will seize that line and also output a 'cozy tone'. The 'cozy tone', is of a pulsed nature and during the quiet periods the central control receiving station listens to the line 14 to detect any signal being emitted by the caller. The central control receiving station detects the 'cozy tone' being emitted by the call unit, and sends a [request ID] message. The tone decoder 46 detects this message and signals it to the microcontroller 24. The call unit now sends an [ID] message. The [ID] message comprises five parts: a. Start character b. Unit identity c. Alarm type d. Message type e. Data checksum On receipt of the [ID] message the central control receiving station transmits an [acknowledge] message. At this stage the central control receiving station will look-up the corresponding data in the database and will indicate the presence of the call to the central control receiving station operators together with the associated data records. It will also display the type of alarm, but only within the limited range of alarm types available within the standard communication protocol. For example "Pendant". When a central control receiving station operator 15 accepts the call, by operating a central control receiving station console, an [operator listen] message is sent to the call unit. On receipt of the [operator listen] message by the call unit it will activate its speech encoder 48 and play a pre-recorded verbal message announcing the type of alarm which initiated the call. For example it might announce "Pendant number one". This message would be announced four times to ensure the central control receiving station operator receiving it. On completion of the announcements the microphone 34 and voice amplifier and voice switches 30 would be activated so that the central control receiving station operator could hear the user. When the central control receiving station operator wants to speak to the user they would press their speak button and the central control receiving station would transmit an [operator speak] message. On receipt of the [operator speak] message the call unit would switch between microphone 34 and loudspeaker 36 so that the user could hear the central control receiving station operator. When the central control receiving station operator wishes to again listen to the user they would release 16 the speak button and the central control receiving station would send another [operator listen] message. On receipt of this message the call unit would switch between loudspeaker 36 and microphone 34 and the central control receiving station operator would again hear the user. The use of the speak button, by the central control receiving station operator, could continue as long as the central control receiving station operator wished. If a further alarm occurred during the conversation, for example a smoke detector went off, the following would happen. The call unit would wait for an [operator listen] message from the central control receiving station. On receipt it would deactivate its microphone 34, loudspeaker 36 and voice amplifier and voice switches 30 and would enable its speech encoder 48. The speech encoder 48 contains a stored vocabulary of words and/or phrases used in all verbal messages that are likely to be used. In response to a sequence of instructions from the controller 24, the speech * encoder 48 emits the selected words in sequence to construct the predetermined verbal message, announcing 17 for example "Smoke - zone 3". This message would be announced four times to ensure the central control receiving station operator receiving it. On completion of the announcements the microphone 34 and voice amplifier and voice switches 30 would be activated so that the central control receiving station operator could hear the user. Any further alarms would be announced in a similar way. Once the central control receiving station operator decided to finish the call, they would enter the appropriate command at the console and the central control receiving station would send a [finish] message to the call unit. On receipt of this message the call unit would drop the line and return to a quiescent state, ready for reuse as a telephone or alarm unit. The central control receiving station would also drop the line and await further calls. The system enables pre-determined verbal messages to be announced to a respondent using a simple telephone in the same way as announcements to a control centre operator once they had selected a call as described above. This facility is illustrated in Figure 4, and enables the provision of information, possibly in response to spoken questions, and information about a 18 multiplicity of alarms rather than one alarm only at the beginning of a call. The user then having initiated an alarm and being in contact with either a centre operator or a respondent is able to initiate an announcement of any one of a number of pre-recorded words or phrases to communicate to the centre operator or respondent. This is done by pressing a key or combination of keys to select the desired message. The key sequence entered into either the control unit keypad 44 or the pendant keypad 56 is interpreted by the microcontroller 24 which initiates a sequence of individual words and phrases to make up the intelligible message required. This facility would be of assistance to any user with impaired speech. In the second embodiment, a bridge rectifier 81 is connected across the public switched telephone network (PSTN) and provides a direct current supply of approximately 50 volts. The current drawn from these PSTN must be very low to satisfy the telephone network providers' specification and is limited to approximately 30 micro-amps by a 2.2 megohm resistor 82. After the resistor 82, a zener diode 83 is connected in a line to earth to regulate the voltage to about 8 volts. After the zener diode, a capacitor 19 84 is also connected to earth. The capacitor may be a 10 microfarad capacitor. A switch 86 is then provided to make and break the seizing circuit. While the circuit is broken, the capacitor 84 will charge to provide a small amount of energy storage. After the switch 86 is provided a diode 95, a resistor 87 and a diode 88 leading the base of a darlington transistor 89. The diodes 95 and 88 may be 1N 4148 diodes and the resistor 87 may be a 100 kiloh resistor The emitter of the darlington transistor 89 is connected to earth and the collector is connected through a further resistor 93 to the base of a second darlington transistor 90. The resistor 93 may be a 10 kilohm resistor. A diode 91 is provided between the collectors of the two transistors forming the darlington transistor 90 and the collector of the darlington transistor 90 is connected to a shunt regulator 98 which is earthed. The diode 91 may also be a 1N 4148 diode. The emitter of the second darlington transistor 90 is connected to the output of the rectifier bridge before the resistor 82 and is also connected to its own base through a resistor 92 which may be a 470 kilohm resistor. The line from the collector of the second darlington transistor 90 to the shunt regulator 98 is also connected to a 5 volt regulator 97 which is earthed and has an output connected through a diode 85 to a point between the 20 capacitor 84 and the switch 86 and which is also connected to a microcontroller 96. The diode 85 may be a 1N 4148 diode. The microcontroller 96 is connected to the circuit between the diode 88 and the second darlington transistor 89 through a line including a resistor 99. This line is also connected before the resistor 99 to earth through a further resistor 100. A line also passes from after the switch 86 through the microcontroller to an opposing diode 94. The power derived from the PSTN is switched via the alarm switch 86 and flows via diode 95 resistor 87 and diode 88 to turn on the first darlington transistor 89 which in turn turns on, via resistor 93, the second darlington transistor 90. The darlington transistor completes the seize current path which is connected directly across the PSTN. The PSTN is thus connected through the rectifier bridge 81, darlington transistor 90, and the diode 92 to the shunt regulator 98 which effects seizing of the telephone line. Once the telephone line has been seized, power is taken from it via the 5 volt regulator 97 and this supplies power to the microcontroller 96. Once the microcontroller 96 is powered up, it takes over control of the telephone line seize circuit by driving 21 the darlington transistors via resistor 99. It is thus able to keep the telephone line seized and also break it to effect pulse dialling. The microcontroller constitutes the aforesaid "autodialler". The microcontroller 96 can also inhibit further unwanted control of the line seize circuit by the alarm switch 86, over-riding it by clamping any signal from it via opposed diode 94.

Claims: 22 CLAIMS 1. The combination of a call unit for an emergency call system incorporating means for transmitting and receiving speech and/or data via the public switched telephone network (PSTN), in a hands-free mode, with a remote trigger device to be carried or worn by the user and including a control input device connected to a signal transmitter for remote operation of the transmitting and receiving means. 2. The combination as claimed in claim 1, wherein the transmitting and receiving means comprises a telephone unit. 3. The combination as claimed in claim 1 or claim 2, wherein the transmitting and receiving means includes an autodialler. 4. The combination as claimed in claim 3, wherein the autodialler is arranged automatically to dial a plurality of different destinations in a pre¬ determined order. 5. The combination as claimed in any preceding claim, wherein the call unit is arranged to transmit at least one verbal message from a store. 23 6. The combination as claimed in claim 1, 2 or 3, wherein the control input device is a keypad. 7. The combination as claimed in any preceding claim, wherein triggering of the remote trigger device through the control input device can be cancelled within a pre-alarm period immediately following triggering. 8. The combination of a call unit with a remote trigger device substantially as described herein with reference to the accompanying drawings. 9. An emergency alarm system including the combination of a call unit with a remote trigger device as claimed in any preceding claim. 10. An emergency call system substantially as described herein with reference to the accompanying drawings. 11. A telephone line seizing system comprising an actuating circuit and a seizing circuit, the actuating circuit comprising means for limiting current drawn from the public switched telephone network (PSTN), first switch means to make and break the actuating 24 circuit and second switch means actuated by the actuating circuit to complete the seizing circuit and thereby seize the telephone line. 12. A telephone line seizing system as claimed in claim 11, wherein a rectifier is provided to rectify current from the PSTN. 13. A telephone line seizing system as claimed in claim 11 or claim 12, wherein the means for limiting current is a resistor having a resistance of at least 2.2 megohms. 14. A telephone line seizing system as claimed in claim 11, 12 or 13, wherein means is provided for increasing the said limited current supplied to the second switch means. 15. A telephone line seizing system as claimed in claim 14, wherein the means for increasing the limited current comprises a darlington transistor. 16. A telephone line seizing system as claimed in any of claims 11 to 15, wherein the second switch means comprises a darlington transistor. 17. A telephone line seizing system as claimed in any 25 of claims 11 to 16, wherein a capacitor is provided before the first switch means to store energy to be used when the first switch means makes the actuating circuit to actuate the second switch means and thereby result in seizing of the telephone line. 18. A telephone line seizing system as claimed in any of claims 11 to 17, wherein an autodialler is provided arranged to be powered by the PSTN when the line has been seized. 19. A telephone line seizing system as claimed in claim 18, wherein means is provided to prevent repeated operation of the first switch means from interfering with the autodialler. 20. A telephone line seizing system as claimed in claim 19, wherein the means to prevent repeated operation of the first switch means comprises a diode capable of clamping the signal. 21. A telephone line seizing system seizing system substantially as described herein with reference to Fig. 5 of the accompanying drawings.

Inventors: CROMPTON STEVEN PAUL, HENLEY MICHAEL, JOHNSON DUNCAN MILES, CROMPTON, STEVEN, PAUL, HENLEY, MICHAEL, JOHNSON, DUNCAN, MILES
Applicants: MODERN VITALCALL LTD, MODERN VITALCALL LIMITED
Application year: 1992
Main classification: H04M19
IPC codes: H04M11, H04M19