Abstract:
The present invention is an alarm system comprising an alarm handset ( 10 ) having a housing ( 30 ), a detector circuit ( 100 ) having means ( 102, 104 ) for receiving a preselected signal from a remote transmitter ( 40 ) and generating a first detection signal in response thereto, first sensing means for sensing change in a preselected parameter of the handset, warning means ( 300 ) for generating a warning signal, alarm means ( 400 ) for generating an alarm signal and control means ( 500 ) responsive to receipt of the detection signal to activate the alarm means ( 400 ). The control means ( 500 ) is operable to activate the warning means in response to at least one of receipt of the control signal and sensing of the change in the preselected parameter of the handset.

Description:
BACKGROUND 
       [0001]    The present invention relates to an alarm system and particularly, but not exclusively, to an improved form of alarm system for detecting smoke, fire, carbon monoxide or other noxious gases. 
         [0002]    The use of carbon monoxide, smoke and fire detectors in homes has become increasingly common. Some systems have a number of remote sounders which can be triggered to emit a warning sound when a remote base station detects the presence of fire, smoke, carbon monoxide or the like. Such a remote sounder has the advantage that it can be placed at the bedside of, for example, a child. 
         [0003]    However, research has shown that children particularly can be difficult to wake and often when they are woken by an alarm the main electrical system of the building may have been damaged and be inoperative and the room or a building may be filled with an appreciable quantity of smoke. The effect is to disorientate the occupants who can then find it difficult to escape from a dark, smoke filled area. This problem can be exacerbated if the fire occurs after dark. 
         [0004]    The present invention seeks to provide an improved alarm system. 
         [0005]    Accordingly, the present invention provides an alarm system comprising: an alarm handset having: a housing; a detector circuit having means for receiving a preselected signal from a remote transmitter and generating a first detection signal in response thereto; first sensing means for sensing change in a preselected parameter of the handset; light generating means for generating visible light; alarm means for generating an alarm signal; and control means responsive to receipt of said detection signal to activate said alarm circuit; wherein said control means is further operable to activate said light generating means in response to receipt of said control signal and subsequent sensing of said change in said preselected parameter of the handset. 
         [0006]    In a preferred form of the invention said preselected parameter comprises one of a preselected time period following receipt of said control signal; actuation of a switch; or movement of said handset. 
         [0007]    Advantageously, said system further comprises: cradle means for supporting said handset; and wherein said first sensing means comprises means for sensing the presence or absence of said handset in said cradle; and said control means is operable to activate said light generating means in response to said first sensing means sensing subsequent removal of said handset from said cradle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present invention is further described hereinafter, by way of example, with reference to the accompanying drawings, in which: 
           [0009]      FIG. 1  is a perspective view of a preferred form of alarm handset according to the present invention; 
           [0010]      FIG. 1   a  is a perspective view of a base station or alarm for use with the handset of  FIG. 1 ; 
           [0011]      FIG. 2  is a perspective view of a cradle for the handset of  FIG. 1 ; 
           [0012]      FIG. 2   a  is a perspective view of the cradle partially broken away to show the internal construction; 
           [0013]      FIG. 3  is a block functional diagram illustrating the operation of the handset of  FIG. 1 ; 
           [0014]      FIG. 4  is a schematic circuit diagram of the circuit of  FIG. 3 ; 
           [0015]      FIG. 5  is a first signal pattern for a first mode of operation of the system of  FIG. 1 ; 
           [0016]      FIG. 6  is a second signal pattern for a second mode of operation of the system of  FIG. 1 ; 
           [0017]      FIG. 7  is a third signal pattern for a third mode of operation of the system of  FIG. 1 ; 
           [0018]      FIG. 8  is a fourth signal pattern for a fourth mode of operation of the system of  FIG. 1 ; and 
           [0019]      FIG. 9  is a fifth signal pattern for a fifth mode of operation of the system of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Referring to the drawings,  FIG. 1  shows a portable handset  10  of a preferred form of alarm system according to the present invention and  FIG. 1   a  shows a base station  40  for the handset. 
         [0021]      FIGS. 2 and 2   a  show a cradle  20  which supports the handset  10 . 
         [0022]    The cradle  20  has a power supply cable which connects the handset to mains  27  via a converter (which may be a transformer or other form of voltage reduction device) which serves to step down the mains supply to a suitable voltage and current which can be used to charge a rechargeable battery in the handset  10  by way of suitable electrical contacts in the handset which connect with co-operating contacts in the base of the handset  10  when the latter is supported in the cradle  20 . This is a conventional arrangement which is used with, for example, portable telephones and will not be described further in detail. 
         [0023]    Referring now to the handset  10 , this has a housing  30  which contains the main circuitry  32  as shown in  FIGS. 3 and 4 .  FIG. 4  is a circuit diagram of the handset circuitry whilst  FIG. 3  is a block function diagram showing the manner of operation of the handset. 
         [0024]    The main circuitry  32  comprises a detector circuit  100 , a sensing means or connection detect circuit  200 , light generating means  300 , alarm means  400  for generating an audible alarm signal, control means  500  for controlling the light generating means  300  and the alarm means  400  and a power supply circuit  600 . 
         [0025]    The handset  10  co-operates with a base station  40  which has a detector which detects radiation, noxious gases and/or air pollutants such as smoke, carbon monoxide and the like and in response to the detection generates a signal representative of the type of radiation and/or air pollutant which is detected and transmits the signal via a transmitter to the handset  10 . 
         [0026]    The handset  10  will normally be located in the cradle  20  and will receive the signal transmitted by the base station  40  through its detector circuit  100 . 
         [0027]    The detector circuit has an aerial  102  and an RF (radio frequency) receiver  104  which detects the transmitted signal and analyses the signal to determine whether or not it is from the base station  40 . 
         [0028]    If the signal is identified as a legitimate signal a code within the signal is extracted by a code extraction circuit  106 . The code can be in the simple form of a pulse modulation signal by which the RF signal transmitted from the base station  40  has been modulated. The code is then passed to a code identification circuit  108  which compares the code with a number of previously stored codes to identify the code. 
         [0029]    If a number of base stations  40  are used in proximity to one another each can be programmed to transmit a unique coded signal so that the code identification circuit  108  can identify the base station triggering the alarm. This is particularly useful in large buildings where the base station will identify the location of the cause of the alarm within the building. The code extraction circuit  106  can generate a pre-selected signal in response to the particular code of signal received from a base station and this signal can result in the audible alarm  400  indicator, LED&#39;s  304  and/or the white LED&#39;s  302  being energised in pre-selected patterns to provide an indication of the type of alarm that has occurred. 
         [0030]    Each base station  40  can also be programmed to emit a unique coded signal in dependence on the type of radiation or pollution which is detected so that, again, the user of the handset can immediately identify the cause of the alarm. 
         [0031]    It is also possible for the base stations to be programmed to transmit a further unique coded signal when the base stations are being tested and this signal again can identify to a user of the handset the fact that the alarm system is being tested and the alarm is not a genuine alarm. Once the code has been extracted from the received signal by the code extraction circuit  106  the code identification circuit then decodes to the code to provide an alarm signal representative of the type of alarm being generated by the system and this signal is then passed to the control circuit  500 . 
         [0032]    The code identification circuit  108  and the control circuit  500  are all part of a microprocessor  700  ( FIG. 4 ) or the like. 
         [0033]    The handset  10  has two power sources as can be identified by the power supply circuit  600 . 
         [0034]    The first power source is mains power as described earlier. The power supply circuit  600  has an external supply connector which is formed by contacts  602  formed on the base of the handset  10  and which connect with the corresponding connectors of the cradle  20  to connect to the external supply  27 . When the handset  10  is mounted in the cradle  20  the sensing means  200  detects the electrical connection of the handset  10  with the cradle  20  and applies a sensing signal to an input circuit  502  of the microprocessor  700 . Although the sensing of the mounting of the handset in the cradle  20  is conveniently by way of the power supply connections  602 , it can also be effected by an suitable means such as a separate switch actuated when the handset is engaged into or removed from the cradle  20 . 
         [0035]    The power supply circuit  600  also has a power supply detection circuit  604  which detects the supply of power from the cradle  20  to the handset  10  by way of the connections  602 . This occurs when the cradle  20  is connected to the external supply by way of the cable and converter and the detection circuit  604  applies a supply detection signal also to the input circuit  502  of the microprocessor  700 . As can be seen from  FIG. 4 , the detection circuit  604  is conveniently simply a resistance divider which applies a voltage to an input of the microprocessor  700  when supply voltage is applied to supply line  612  of the main circuitry  32 . 
         [0036]    Power is also supplied from the supply connector  602  to a regulation and protection circuit  606  and by way of a supply switching circuit  608  (in the form of diodes) to provide the supply for the circuitry  32  of the handset  10 . 
         [0037]    The regulation and protection circuit  606  regulates the supply and provides protection for the handset circuitry against fluctuations and voltage surges or peaks in the mains supply, as well as connection of the wrong form of supply, e.g. ac or wrong polarity or voltage. 
         [0038]    A battery  610  is also connected to the regulation and protection circuit  606  and supplies power for the handset circuitry  32  in the absence of the external supply. The battery can be a rechargeable battery which is recharged by the power supply circuit  600  when the external supply is connected. 
         [0039]    The input circuit  502  of the microprocessor  700  receives the decoded alarm signal, the sensing signal and the supply detection signal and processes these to provide a control signal to the light generating means  300  and/or the audible alarm  400 . The microprocessor  700  also has a pattern generator circuit  504  and drivers  506  for driving the indicator LED&#39;s  304 . The audible alarm  400  and the white LED&#39;s  302  have their own drivers respectively  406 ,  306 , which are controlled by the pattern generator circuit  504 . 
         [0040]    As can be seen from  FIG. 3  the light generating means  300  has one or more white LEDs (light emitting diodes)  302  and indicator LEDs  304 . The audible alarm  400  conveniently consists of a buzzer or other suitable means for generating an audible alarm signal. 
         [0041]    The indicator LEDs  304  can comprise a number of different coloured LEDs e.g. green and red, which can be arranged to flash in various sequences as described further below. 
         [0042]    When the base station  40  generates an alarm signal this is transmitted to the handset  10 . The signal is then processed and decoded by the detector circuit  100  and the decoded alarm signal is applied to the input circuit  502  of the control circuit  500 . 
         [0043]    At the same time, the input circuit is also in receipt of a signal from the connection detect circuit  200  which indicates whether or not the handset is stored in its cradle  20 . 
         [0044]    If the signal received from the base station  40  indicates that the base station is being tested then the alarm signal from the identification circuit  108  is processed by the control circuit  500  to energise one or more of the indicator LEDs  304  in a preset pattern to indicate that the system is being tested. It is also possible in this situation for the control circuit to energise the audible alarm  400  at a relatively low level and in a preset pattern. 
         [0045]    If the alarm signal applied to the control circuit  500  indicates that there is an alarm then the control circuit will energise the buzzer  400  to provide an audible alarm. In addition, the white LEDs  302  will be energised in a preselected sequence. 
         [0046]    The audible alarm tone generated by the buzzer  400  will commence and increases over time to a maximum level. In one form of the invention the alarm tone is held at a first volume level for a first preselected time period, typically ten seconds. The volume level is then raised and the alarm continues for a further preselected time period, again typically ten seconds. This sequence continues with the volume of the alarm being increased at the end of each preselected time interval until the handset is removed from the cradle  20 . At this point the signal supplied by the detect connection circuit  200  to the input circuit  502  changes, resulting in the audible alarm  400  being deactivated or the drive signal being changed to cause the audible alarm to emit a further, preselected sound pattern which is indicative of the fact that the handset has been removed from the cradle  20 . The microprocessor  700  may also be programmed to issue voice commands or instructions after pick up of the handset  10  from the cradle. These could be, for example, instructions on how to evacuate the building. The audible alarm which is generated prior to pick up of the handset could also be a voice, which issues simple commands such as “fire”, as increasing volume levels. 
         [0047]    If the handset  10  remains in the cradle  20 , the audible alarm  400  will continue to be sounded for a total period of four minutes. At this point, if there is no signal detected by the detector circuit  100  the system will reset. 
         [0048]    Either the handset  10  or the cradle  20  could be connected to a vibration device (such as a vibration pillow) by suitable means such as a cable or radio signal. This can be controlled by the microprocessor  700  such that in addition to or as an alternative to the audible alarm  400  and/or the lights  302 ,  304  being energised, the vibration device could be energised to wake a sleeping person. 
         [0049]    The microprocessor  700  is programmed to energise the audible alarm  400  and light generating means  300  in preselected patterns in dependence on the type of signal received from the identification circuit  108 . Thus, the energising of one or more of the audible alarm  400  and light generating means  300 , can indicate the type of alarm being generated. It is also possible for the detector circuit  100  to receive several signals that runs from either a number of different base stations or the same base station which has detected several different alarm situations. For example, the base stations can monitor carbon monoxide levels and other noxious gasses, smoke and other particles in the air and radiated heat. It is also possible for one base station to detect one or more of these and transmit several different alarm signals. 
         [0050]    Where the identification circuit  108  identifies two or more different alarm signals and applies these to the input circuit  502 , the microprocessor can process the received signals to energise the audible alarm  400  and/or the light generating means  300  in a further preselected pattern, to indicate the fact that two or more alarm conditions exist. Alternatively, the microprocessor can be programmed to prioritise the alarms and identify which of the alarm signals received indicates the more dangerous alarm condition, and indicate this by suitable energising of the audible alarm  400  and/or light generating means  300 .  FIG. 5  shows a typical drive signal for the audible alarm  400  in which the alarm is pulsed on and off for 0.5 second periods with a 1.5 second pause between each group of pulses. This signal is typically used when the signal from the base station  40  indicates that the base station has detected smoke or excess heat which could indicate a fire. 
         [0051]    Where the base station  40  detects carbon monoxide or other noxious gasses the driver signal applied to the audible alarm  400  is typically in the form shown in  FIG. 6  with a much higher repetition frequency of 0.1 seconds on and 0.1 second off with a pause of 5 second between each group of pulses. 
         [0052]    The colour or pattern of indicator LEDs  304  can also be varied to indicate the type of alarm. 
         [0053]    When the handset  10  is removed from the cradle  20  after an alarm has been initiated, the sensor means  200  detects this and applies a corresponding signal to the input circuit  502 . This cancels the alarm phase actuation of the buzzer (or alternatively causes actuation of the buzzer to generate a different, preselected sound pattern)  400  and causes energising of the white LEDs  302  which provide a “torch” function to enable the user to find his way through the building in the absence of any other lighting. The energising of the indicator LEDs  304  can also be cancelled at the same time. 
         [0054]    It is advantageous to maintain the activation of the audible alarm  400  but at a set volume and energising or “locator” pattern since this acts as a “homing” signal or locator for the emergency services should the handset user be overcome or unable to find a way out of the building. 
         [0055]    The indicator LEDs  304  can also provide an indication of the level of battery power available regardless of whether or not the handset  10  is removed from the cradle  20  or availability of the external power supply. 
         [0056]    If the handset  10  is removed from the cradle  20  in the absence of an alarm signal, the detect connection circuit  200  detects this removal and applies a signal representing this to the input circuit  502 . The control circuit  500  then activate the buzzer  400  to generate a preselected sound pattern such as that shown in  FIG. 9  to indicate that the handset  10  has been removed from its cradle  20 . Return of the handset  10  to the cradle  20  cancels the signal. 
         [0057]    In order to prevent unwanted tampering of the handset the control means may be configured, in the circumstance where no RF signal is received, to give only an audible alarm signal (no light) for several minutes when removed from the base until the handset is replaced. This is to stop the handset being used as a torch or a toy. If the handset is left out for a prolonged period of time it could be set to chirp periodically to alert someone but not completely discharge the battery (as it would in full alarm mode). 
         [0058]    Alternatively, in the event the AC power fails the light on the handset could illuminate slightly (like a night light, so as not to awaken unnecessarily) and then on removal (again, in the event no RF signal is received) the handset becomes an emergency torch (i.e. full brightness). 
         [0059]    The handset can also be programmed to enter a power save mode where the control circuit changes the polling of the alarm sensing to save power while still maintaining an acceptable reaction time. The microprocessor  502  can switch the circuit into “sleep” mode for a preset period of time before switching back to “wake” mode and checking to see if an alarm signal is received. If no signal is received the circuit is switched back into “sleep” mode for a further time period. 
         [0060]    An LCD display (not shown) can also be provided on the handset to display information, typically non-critical information, such as a low battery indicator. 
         [0061]    If the handset  10  is not fitted to its cradle when an alarm signal is received from the base station  40  the handset circuitry operates in the same way as if the handset were mounted in the cradle  20  but the audible alarm is activated by the control circuit  500  for a preset period of time following which it then switches the audible alarm  400  into a locating sound pattern and energises the white LEDs  302 . 
         [0062]    If, after an alarm is generated and the handset  10  removed from the cradle  20 , the handset  10  is replaced in the cradle  20 , the detect connection circuit  200  detects this and applies a signal to the input circuit  502 . This results in the microprocessor cancelling the alarm signal applied to the energising of the buzzer  400  and white LEDs  302 . If, however, an alarm signal is again detected by the detection circuit  100  the alarm will again be activated as described above. 
         [0063]    The system can also be switched in to a “learn” state. 
         [0064]    A “learn” switch  60  can be closed to connect a pin of the microprocessor  700  to ground. When the microprocessor detects this, it switches into a “learn” state for a preselected time period. When the handset is in its learning state, any alarm signal which is received by the receiver  104  is processed by the code extraction circuit  106 . The extracted code is then stored in a memory or store  510  in the microprocessor  700 . 
         [0065]    The handset has two learning states, a full learning state and an incremental learning state. 
         [0066]    The incremental learning state is initiated by pressing the learn switch  60  for a time period less than a pre-selected time, typically five seconds. This causes the control circuit  500  to generate a pre-selected light and/or audible pattern with the LED&#39;s  302 ,  304  or buzzer  400  to indicate that the handset is in its incremental learning state. The base unit  40  is then self-tested and generates a unique coded alarm signal, which is then detected by the handset, as described previously, and is stored in its memory  510 . When the alarm signal is detected, the microprocessor generates a different visual and/or sound pattern to indicate that an alarm signal has been received and the code stored. 
         [0067]    The handset then remains in the incremental learning state for a further pre-selected period of time. If no alarm signals are received from any further base units during that period, then the handset exits the incremental learning state. The incremental learning state can also be cancelled by returning the handset into its cradle  20 . 
         [0068]    When the handset receives the alarm signal, before storing the extracted code, this is compared with codes already stored in the microprocessor memory  510 . If this shows that the relevant base station has already been identified and its unique alarm signal stored, the extracted code signal is ignored. To enter the full learning state, the learn switch  60  is held closed for longer than a pre-selected time period, again typically five seconds, following which the handset enters its full learning state. The microprocessor then energises one or more of the white LED&#39;s, indicator LED&#39;s and buzzer to indicate that the handset is in its full learning state. In this state, the microprocessor erases all of the previously stored signals in its memory  510  and generates a confirmation sound or beep from the buzzer  400  when it is ready to detect new base station alarm signals. The handset then proceeds to “learn” any new signals received in the same manner as in the incremental learning mode. 
         [0069]    The control circuit  500  can also re-transmit any received alarm signals either by wire or wireless to enable the handset to act as a hub or gateway to other systems. The re-transmitted signal can also use a protocol such a Bluetooth, ZigBee or WiFi. 
         [0070]    To encourage use of the handset by children, it may conveniently be combined with, for example, a mobile phone or MP3 player. 
         [0071]    Whilst the use of the handset  10  has been described in combination with a cradle, the latter is not essential to the invention. Movement of the handset  10 , i.e., when it is picked up after generating an alarm signal, can be detected by a movement sensor, which then causes the microprocessor to switch the handset into its alarm state, in which the white LED&#39;s  302  are energised at a constant light level and the audible alarm  400  is energised into the locating sound pattern.