GB2193061A - Emergency call acceptor - Google Patents

Abstract

An emergency call acceptor for use in the receipt of emergency calls via a telephone system from a remote emergency call unit comprises electrical connection means (10) whereby the acceptor may be connected to the telephone system in parallel with an ordinary telephone instrument, an electronic tone generator circuit and a plurality of manually operable switch means (11-13), operation of each switch means controlling the tone generator circuit to cause the circuit to generate an audio frequency tone signal specific to the respective switch means and to apply that tone signal to the connection means for transmission over the telephone system to the remote emergency call unit. <IMAGE>

Description

SPECIFICATION Emergency call acceptor The invention relates to call receiving devices for use in emergency call systems, typically for the elderly and/or infirm.

Emergency call systems for the elderly and infirm are becoming widespread, both in sheltered housing schemes and in ordinary residential locations. In a typical application to an ordinary residential location, i.e. an ordinary dwelling occupied by an elderly or infirm person, an emergency call raising device, or call unit, is usually connected to the subscriber telephone line serving the dwelling in question.

The call unit incorporates an automatic dialling device actuated in response to an external stimulus to dial a call on the public telephone network. Details of an exampie'of such a call unit have been given in our co-pending patent application number GB 2166321.

Foilowing establishment of a connection with a control centre at some remote location, which is suitably equipped and staffed to receive emergency calls and summon assistance for the caller, the call unit transmits data identifying the origin of the call. This data is decoded and displayed or printed at the control centre, informing the staff of existence of an emergency situation at a specific old person's home, and enabling them to summon assistance for the caller.

Initiation of the emergency call may be by specific actuation of a push-button or pullswitch, by an environmental detection unit, e.g. a smoke detector, by a device responsive to a period of inactivity in the dwelling, or by a remote trigger device carried by or kept within reach of the protected person, e.g. a radio, infra-red or ultrasonic transmitter.

In addition to transmission of data, some emergency call systems also incorporate a two-way speech facility, enabling the staff at the control centre to ascertain the nature of the emergency by conversing with the caller.

Such a speech facility normally provides 'hands-free' half-duplex loudspeaking operation, generally with'the speech direction manually switched by the operator at the control centre. A further refinement involves transmission, decoding, and display to the control centre staff of codes identifying the manner in which the call was raised, i.e. whether raised, for example, by a smoke detector, body-worn remote trigger device, or inactivity monitor.

As a precaution against accidental disconnection of the call by the caller, calls may generally only be disconnected by the staff at the control centre.

Typically, the call unit incorporates a memory device in which are stored one or more telephone numbers of locations to be dialled when the call unit is used to raise an emergency call. The telephone numbers are 'programmed' into the device before it is introduced to service, typically by setting banks of switches or installing a solid state memory device, e.g. a PROM. Where more than one telephone number is stored, the first number is that of the control centre at which calls are normally to be received. The second and subsequent numbers are those of alternative call destinations, and are automatically tried in accordance with some prescribed re-dialling sequence in the event of a call attempt to the first number failing.

When a person in distress raises an emergency call, automatic dialling of the control centre is initiated. The equipment at the control centre detects ringing voltage on the telephone line and loops the line. The call unit meanwhile has started to transmit a 'junk tone', this being an intermittent burst of tone specified by the authority administering the telecommunications network, which constitutes the first phase of the 'handshake' procedure whereby automatic calling and receiving equipment exchange signals to establish that the call has reached the correct destination before transmission of information commences. The receiving equipment then sends an 'answer tone' to the call unit. On receipt of the answer tone, the call unit starts to transmit its identification data.When the data has been successfully decoded and displayed at the control centre, the control centre sends a 'kiss off' tone, and the speech channel is opened for dialogue between the caller and the control centre operator. The operator generally presses a 'press to talk' switch which causes a speech direction control tone to be sent to the call unit, causing the call unit's speech equipment to be switched so as to transmit speech in the direction from thk- control centre to the call unit. Releasing the 'press to talk switch' causes a further burst of speech direction control tone to be sent, giving rise to reversal of the call unit's speech equipment, enabling speech signals to be transmitted from the call unit to the control centre.Finally, on completion of the call, the operator at the control centre operates a 'cleardown' button, giving rise to transmission of a tone to the call unit which, when received causes the call unit to unloop the line, thus disconnecting the call. The junk tone must be transmitted in the form prescribed by the telecommunications authority administering the network, but it will be understood that the other control signals mentioned in the foregoing may take various forms, for example bursts of tone at a prescribed frequency, a particular frequency being interpreted by the equipment as an instruction to perform a particular function, (d.g. reverse speech direction, terminate call).Alternative methods of transmitting the control signals may be used, for example in modern telecommunications practice, two frequencies from a range of available single-frequency tones are combined to form 'dual tones', each combination of two frequencies representing a particular command or item or information.

Various types of control centre equipment are known, ranging from a battery-powered desk-top device, through more complex 'console' equipment providing greater call handling capacity, to large computer-controlled installations whereby emergency calls arriving on multiple telephone network connections are handled by multiple operators, with the status of call traffic continuously displayed on the screens of video terminals, and call handling effected by way of the operators' terminal keyboards. Regardless of its nature, the call receiving apparatus is inevitably complex through having to incorporate equipment for sending and receiving control tones, decoding and displaying data, and amplification, direction-switching and reproduction of speech.In addition, complex control electronics are essential in large capacity systems capable of simultaneous handling. of calls arriving on several lines.

Althdugh in a conventional application of emergency call equipment such as that described above, calls are receiving at an emergency control centre, operated typically by an organisation providing welfare services for the elderly and infirm, the need can arise for emergency calls to be received at a private dweiling-typically the home of a friend or relative of the old or infirm person protected by the- call unit. The circumstances in which such a need could arise are diverse, ranging from, for example, default of payment of fees to the control centre administration, to provision of a 'back up' call receiving facility as a precaution against possible inefficient or unreliable operation of the- control centre.Alternatively, the user of the call unit may simply wish to combine the specialised operating facilities of the call unit, e.g. remote call raising with a bodyworn trigger device and 'handsfree' loudspeaking operation, with reception of calls at the home of a friend or relative. Since the connection of an emergency call involves an exchange of 'handshaking' signals and the transmission of data, as described in the foregoing, an ordinary telephone instrument located at the home of a friend or relative of the protected elderly or infirm person cannot be used to receive calls from the specialised emergency call units. Furthermore the complexity of specialised receiving equipment, as described in the foregoing, would render such equipment prohibitively costly for purchase by a private individual.

The object of the invention is to enable emergency calls originating from specialised emergency communication equipment to be answered on an ordinary telephone by connecting a simple and inexpensive emergency call acceptor device to the telephone line in parallel with the telephone. No specialist in stallation work is involved, the emergency call acceptor and telephone being connected in common to the telephone line jack using a two-way adaptor plug. It will be understood that whilst a single call receiving installation of the type referred to in the foregoing serves as a central call answering facility for calls origi nating from call units in the homes of numer ous aged and infirm people, the emergency call acceptor described here is intended mainly for receipt of emergency calls from a single origin.The possibility of using the emergency call acceptor for receiving calls from more than one origin is however not excluded.

According to a first feature of the present invention, we provide an emergency call ac ceptor for use in an emergency call system, comprising an electronic tone generator circuit and a series of manually operable switches, audio frequency tone signals are generated by the emergency call acceptor and output to a subscriber's line of a switched telephone net work to which the emergency call acceptor is connected in parallel with an ordinary tele phone instrument, such that on receipt of an incoming call from a remote emergency call unit, one or more of the switches on the emergency call acceptor are operated so as to place signals on the telephone line which, when received by the emergency call unit, give rise to enablement of the emergency call unit's speech equipment, thereby permitting the ordinary telephone connected in parallel with the emergency call acceptor to be used to conduct a conversation with the user of the emergency call unit.

According to a second feature of the inven tion, operation of one or more switches on the emergency call acceptor subsequent to en abling of the emergency call unit's speech equipment controls the direction of half-duplex speech transmission.

According to a further feature of the inven tion, operation of one or more switches on the emergency call acceptor gives rise to the telephone line being unlooped at the emer gency call unit and the call thus terminated.

Operation of the emergency call acceptor is as follows: When an emergency call is raised on a call unit at the home of an elderly or infirm per son, programmed to dial a call to the home of a friend or relative of the protected person, the ordinary telephone at the home of the friend or relative rings. The friend or relative, lifting the handset, hears the intermittent 'junk tone' transmitted by the call unit, and is thus aware that the call originates from emergency call equipment. Hearing the junk tone, the friend or relative switches- on the emergency call acceptor and presses the CALL ACCEPT button, this action causing an answer tone to be transmitted over the telephone network to the call unit.On receiving the answer tone, the call unit stops sending its junk tone and starts to transmit its identification data in the form, for example, of a series of bursts of DTMF signal, the respective bursts comprising various frequency combinations, and each frequency combination representing a particular item of information, e.g. numeric value or alphabetic character. This data would normally be decoded by the receiving apparatus, but when received on an ordinary telephone is simply heard by the person answering the telephone, and serves no purpose. The friend or relative then presses the CALL ACCEPT button, causing a further control tone to be transmitted, this signal giving rise to termination of transmission of the data and causing the speech equipment in the call unit to be enabled, permitting the caller to address the person answering the call.The switching of the signal generator in the emergency call acceptor is so arranged that when the TALK button is pressed a further tone signal is sent to the call unit, causing the speech equipment in the call unit to be 'reversed' and enabling the friend or relative answering the call to speak to the caller, and when the TALK button is released a further reversal of the speech direction takes place. By pressing and releasing the TALK button in alternation, a conversation can be held between the caller and the person answering the call, the ordinary telephone serving as speech equipment at the call destination.On completion of the conversation, the person receiving the call presses the third button on the emergency call acceptor, marked CLEARDOWN, this action giving rise to transmission of a tone signal interpreted by the call unit as an instruction to unloop the line, thus terminating the call (It will be understood that this last aspect of operation is applicable to a telephone system whereby the call is 'held' by the calling party, i.e. the connection cannot be broken by the called party 'hanging up'). Finally, the person who answered the call replaces the telephone handset and switches the emergency call acceptor off.

It will be understood that of the emergency call acceptor principle illustrated in the foregoing example may be adapted within the scope of the invention for compatibility with the equipment from which calls are to be received in respect of, for example, the form, number, function and marking of the controls on the emergency call acceptor, and the function (e.g.

answer tone, cleardown) and nature (e.g. single frequency, DTMF) of the signals transmitted. Furthermore the emergency call acceptor may be executed in battery-powered form, or be powered from the ac mains or from the telephone line. The physical form of the emergency call acceptor is not restricted to the small piastic case described in the foregoing: the emergency call acceptor unit could, for example, be integrated with the telephone instrument itself, or could be constructed as a base or plinth on which the telephone instrument could stand.

It is also envisaged that the signalling between the emergency call acceptor and the call unit could be so arranged that the initial response from the emergency call acceptor is recognised by the call unit as originating specifically from an emergency call acceptor, the call unit then responding by opening the speech channel immediately instead of first transmitting identification data. It will be understood that since microprocessor control is generally employed in modern call units of the type under consideration here, adaption of the signalling sequence in accordance with the nature of the equipment responding to a specific call can form part of the control algorithm embodied in the call unit's software.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of the emergency call system of which the emerency call acceptor is a part.

Figure 2 is an illustration of the emergency call acceptor.

Figure 3 is a schematic diagram of the emergency call acceptor circuit.

Fig. 1 shows an emergency call system comprising a call unit 1 programmed to dial a call via the public switched telephone network 2 to either an emergency call receiving station (control centre) 3 or to premises 4 at which calls from the call unit may be answered by means of an ordinary telephone 5 in combination with an emergency call acceptor 6. The call unit 1 is normally programmed to make a first call attempt to the control centre 3, with a repeat attempt being made tithe premises 4 with the ordinary telephone 5 and emergency call acceptor 6 in the event of the first call attempt failing. Alternatively, the call unit 1 may be programmed to make a call attempt exclusively to the premises 4 at which the ordinary telephone 5 and call unit 6 are installed.The call unit 6 and telephone 5 are connected in parallel to the normal two-wire telephone subscriber line serving the premises 4.

Fig. 2 shows how the call unit is constructed as a small plastic case 9 with three push-buttons 11, 12, 13 and a cord 10 for the telephone line connection.

Fig. 3 shows how the emergency call acceptor circuit comprises a signal generator of the dual tone multi frequency (DTMF) type 17 with input connections from switching/timing circuits 18, 19, 20, and its output signal fed to the subscriber telephone line to which the emergency call acceptor is connected in parallel with an ordinary telephone. In this example, the dual tone multi-frequency signal generator 17 is executed in the form of an integrated circuit of type MT5089 manufactured by the Mitel company, in accordance with modern practice in the telecommunications equipment industry, but may equally be constructed from discrete components in a manner familiar to a person skilled in the art.Further functional elements of the emergency call acceptor are transient suppressor and polarity correction circuits 14 whereby the DTMF generator 17 is connected to the telephone line, and whose function and construction will be familiar to a person skilled in the art. Power supply to the emergency call acceptor is derived from the telephone line: the polarity correction circuit 14 ensures that the positive and negative lines to the DTMF generator 17 and associated circuitry are fed with the correct polarity regardless of how the telephone line is connected, and the voltage detector and power switch 15 serve to make a power connection between the telephone line and the DTMF generator 17 and associated circuitry when a drop in voltage is detected across the two conductors of the telephone line.The three switch/timer circuits 18, 19, 20 perform the dual function of placing signals on input lines to the DTMF generator 17 when a push-button switch incorporated in each of the switch/timer circuits is operated, and maintaining the input signal for a pre-determined time interval thus causing the DTMF generator 17 to generate a signal for a specified duration, the combination of frequencies of which is particular to the pushbutton operated. Note that whilst the 'call accept' and 'cleardown' switch/timer circuits 18 and 20 cause their particular dual tone to be generated for a specified duration each time the push-button is depressed, the 'talk/listen' switch/timer circuit 19 causes one dual tone to be generated when the switch is depressed, and an alternative dual tone to be generated when the switch is released.The acual form of construction of the individual circuit elements will be apparent to a person skilled in the art, and will not be described in further detail here.

A person present at the premises 4 where the telephone 5 and emergency call acceptor 6 are installed is made aware of the arrival of a call by the telephone ringing. The call may be from any ordinary telephone or from an emergency call unit 1 programmed to raise a call to the telephone number in question. Furthermore, the call unit 1 may, depending on its circumstances of use, dial a call to the premises 4 either as the destination of its initial dialling attempt, as the destination of a repeat dialling attempt in the event of the first attempt to another destination failing, or as the call unit's only call destination.

The person lifts the telephone handset, looping the telephone line and causing the ringing to stop. The line voltage drop associated with the handset being lifted is detected by the voltage detector and power switch circuit 15 in the emergency call acceptor, and power from the telephone line is fed to the functional circuit elements of the emergency call acceptor by way of the voltage regulator 16. The emergency call acceptor is thus automatically switched on.

On completion of dialling, the call unit 1 begins to transmit a 'junk tone' as required by the telecommunications authority controlling the telephone network-typically a repeated burst of tone. This is heard by the person answering the call, who recognises the tone as originating from the call unit 1, and presses the CALL ACCEPT push-button 11 which forms part of one of the switch/timer circuits 18. The switch/timer circuit 18, which incorporates a capacitor to perform the timing function and transistor for switching, places a signal on two of the input lines of the DTMF generator 17, causing the DTMF generator 17 to output a DTMF signal to the telephone line.

This signal, a specified combination of two frequencies, is transmitted to the call unit 1 where it is recognised as an answer tone. On receipt of the answer tone, the call unit 1, operating under microprocessor control, stops sending the junk tone and starts sending identification information, typically as bursts of DTMF tone, a particular frequency combination representing a particular numeric or alphabetic character. These tones are heard by the person answering the call but are in this instance not decoded in any way.On hearing the DTMF tones the person answering the call presses the CALL ACCEPT push-button 11 again, causing a burst of DTMF tone to be sent to the call unit 1 where it is interpreted as a signal to terminate transmission of the data and enable the call unit's half-duplex speech equipment, permitting initially speech transmission FROM the call unit 1 TO the telephone 5. To speak to the caller, the person answering the call presses the TALK pushbutton 12 on the emergency call acceptor 9.

This push-button forms part of the second switching/timing circuit 19 which, in common with the first switching/timing circuit 18, incorporates a capacitor for the timing function and transistors for switching. It is however so contrived that depressing the TALK push-button 12 causes a 'talk' DTMF signal to be generated by the DTMF generator. 17, and release of the TALI < push-button 12 causing a 'listen' DTMF signal to be generated. The 'talk' and 'listen' signals differ with regard to their constituent frequencies, and are recognised by the call unit 1 as instructions to reverse the direction of its half-duplex speech equipment. Thus by pressing and releasing the TALK push-button, the person receiving the call is able to hold a conversation with the caller, the ordinary telephone 5 connected in parallel with the emergency call acceptor 6 constituting the speech equipment at the call destination. On completion of the conversa tion, the person answering the call presses the CLEARDOWN push-button 13 which forms part of the switching/timing circuit 20. This circuit functions in exactly the same manner as the 'call accept' switching/timing circuit 18 but causes a combination of frequencies specific to the call clearing function to be generated by the DTMF generator 17 and output to the telephone line. This DTMF signal, received by the call unit 1, causes the telephone line to be unlooped at the call unit 1, and the call thus terminated. The person receiving the call then replaces the telephone handset, this action causing the telephone line voltage to increase. The line voltage increase is detected by the voltage detector and power switch circuit 15 in the emergency call acceptor 6, and the power supply to the functional elements of the emergency call acceptor cut off. The emergency call acceptor is thus returned to its quiescent state until a further call arrives. In the event of a call being received from an ordinary telephone, the person answering the callwill not hear a junk tone when the handset is lifted, and the call will be taken in the normal manner, without involvement of the emergency call acceptor 6.

Claims (11)

1. An emergency call acceptor for use in the receipt of emergency calls via a telephone system from a remote emergency call unit, the acceptor comprising electrical connection means whereby the acceptor may be connected to the telephone system in parallel with an ordinary telephone instrument, an electronic tone generator circuit and a plurality of manually operable switch means, operation of each switch means controlling the tone generator circuit to cause the circuit to generate an audio frequency tone signal specific to the respective switch means and to apply that tone signal to the connection means for transmission over the telephone system to the remote emergency call unit.

2. An emergency call acceptor according to claim 1 in which each switch means is a single switch.

3. An emergency call acceptor according to claim 1 or claim 2 in which the tone generator circuit is controllable to generate a first audio frequency tone signal enabling acceptance of a call from the remote emergency call unit and the opening of a two-way speech communication facility between that unit and the ordinary telephone instrument.

4. An emergency call acceptor according to claim 1 or claim 2 in which the tone generator circuit is controllable to generate second and third audio frequency tone signals enabling half-duplex speech communication between the remote emergency call unit and the ordinary telephone instrument under control of the call acceptor.

5. An emergency call acceptor according to claim 1 or claim 2 in which the tone generator circuit is controllable to generate a fourth audio frequency tone signal enabling termination of a call from the remote emergency call unit by unlooping the telephone line at that unit.

6. An emergency call acceptor according to any one of the preceding claims in which the tone generator circuit is such that each tone signal is a dual tone multi-frequency signal.

7. An emergency call acceptor substantially as herein described with reference to the accompanying drawings.

8. An emergency call system capable of operation by way of a telephone network, the system comprising an emergency call unit; means for connecting the emergency call unit to the telephone network; alarm means for initiating an emergency call from the emergency call unit; an ordinary telephone instrument remote from the call unit; means for connecting the remote telephone to the telephone network; an emergency call acceptor; means for connecting the emergency call acceptor to the telephone network in parallel with the remote telephone; the emergency call unit including an autodialler, a first electronic tone generator circuit and a microprocessor and being operable in response to operation of the alarm means (a) to autodial the preset telephone number of the remote telephone, (b) on completion of a connection with the remote telephone to transmit an identifying sequence of audio frequency tone signals to the remote telephone, (c) on receipt of an enabling sequence of audio frequency tone signals to open a two-way speech communication facility between the call unit and the remote telephone and (d) on receipt of a termination sequence of audio frequency tone signals to unloop the connection to the telephone system and so terminate the call; and the emergency call acceptor comprising a second electronic tone generator circuit and a plurality of manually operable switch means, operation of respective switch means controlling the second tone generator circuit to generate respectively the enabling sequence of audio frequency tone signals and the termination sequence of audio frequency tone signals for transmission via the telephone network to the emergency call unit.

9. An emergency call system according to claim 8 in which operation of further respective switch means on the emergency call acceptor controls the second tone generator circuit to generate respectively speech control sequences of audio frequency tone signals, and the emergency call unit includes means responsive to the speech control sequences to enable half-duplex speech communication between the emergency call unit and the remote telephone under control of the call acceptor.

10. An emergency call system according to claim 8 or claim 9 in which each switch means of the emergency call acceptor is a single switch.

11. An emergency call system substantially as herein described with reference to the ac companying drawings.