Abstract:
A life safety system with a micro-controller that is programmed to operate both a visual signal and an audible signal. One feature of the system is that a user is permitted to enter a temporal signaling mode for not only the audible signal, but also the visual signal. The program includes an energy saving routine that operates the visual signal in the temporal mode with an energy consumption that is substantially smaller than required for operation in a continuous mode. The temporal pattern has four cycles with one flash pulse per cycle for the first three cycles and no flash pulse for the fourth cycle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a life safety system and method that is energy efficient. In particular, the present invention relates to a life safety system and method for controlling a visual signal in an energy efficient manner. 
     2. Description of the Prior Art 
     Life safety systems are used in and around buildings to alert people of an emergency event, such as a fire or other event that could cause bodily harm. Generally, a life safety system includes one or more visual signals and/or audible signals that are operated to alert people of an emergency event and guide them along an evacuation route. 
     It is known to operate a visual signal in a continuous mode in which the visual signal flashes at a rate in the range of about 0.33 to 3 Hz with one flash per cycle. A continuous mode flashing is not very distinctive and may not sufficiently alert a hearing impaired person of impending danger. Also, such visual signals are designed to operate only in the continuous mode. That is, there is no provision for a user to choose another mode. 
     It is also known to operate an audible signal in either a continuous mode or in a temporal mode. In the continuous mode, the audible signal emits sound bursts at a rate of about 0.33 to 3 HZ with one sound burst per cycle. In the temporal mode, the audible signal operates in a sound pattern of four cycles with one sound burst per cycle for the first three cycles and no sound burst for the fourth cycle. The temporal mode is especially beneficial to the visually impaired person as it provides a distinctive and recognizable warning sound pattern. 
     It is also known to use one or more micro-controllers to control the operation of visual and/or audible signals. For example, U.S. Pat. No. 5,659,287 to Donati et al. provides a life safety system having a micro-controller that operates a visual signal and/or an audible signal based on program routines. The program routines include the capability of operation in a synchronous mode with other micro-controllers in the life safety system such that visual signals controlled by the micro-controllers all flash substantially in unison. The program routines also operate the audible signal in either a continuous mode or in a three pulse temporal pattern. However, the program routines make no provision for the micro-controller to operate the visual signal and the audible signal in synchronism so that a visual flash and a sound burst occur substantially simultaneously. 
     Accordingly, there is a need to provide a user of a life safety system with a choice of choosing a mode other than continuous for a visual signal. There is also a need to control the initiation of a visual signal annunciation and an audible signal annunciation so that they appear simultaneous in time to a person who is subjected to both. There is also a need to provide a distinctive visual flash pattern to a hearing impaired person for emergency event situations. 
     An object of the present invention is to provide a method of operating a visual signal that meets the aforementioned needs. 
     Another object of the present invention is to provide a life safety system that satisfies the above needs. 
     SUMMARY OF INVENTION 
     A method according to the present invention operates a visual signal in a life safety system. The life safety system includes a micro-controller that operates the visual signal to provide a visual alarm signal when an emergency event occurs. 
     The method determines if a temporal mode is set in the micro-controller. If a temporal mode is set, a flash pulse stream is developed that has a repetitive pattern of four cycles with one flash pulse per cycle for the first three cycles of the pattern and no flash pulse for the fourth cycle of the pattern. The flash pulse stream is then applied to the visual signal. The visual signal flashes in a repetitive pattern that includes four consecutive cycles with a flash occurring in each of the first three cycles of the pattern and no flash occurring in the fourth cycle. This eliminates a need for the visual signal to consume energy during the fourth cycle with the advantage that a smaller and less costly power supply can be used. 
     In another aspect of the invention, the micro-controller is controlled to cause the visual signal and an audible signal to flash and sound in unison. 
     A life safety system according to the present invention includes an energy saver program that causes the micro-controller to use the method of the present invention. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference characters denote like elements of structure and: 
     FIG. 1 is a block diagram of a life safety system according to the present invention; 
     FIG. 2 is a waveform diagram illustrating a temporal flashing according to the present invention; and 
     FIG. 3 is a flow diagram of the energy saver program included in the FIG. 1 system. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     With reference to FIG. 1, there is provided a life safety system generally represented by numeral  10 . Life safety system  10  includes a micro-controller  12 , a visual signal  14 , an audible signal  16  and a detector  18 . Micro-controller  12  is coupled with visual signal  14 , audible signal  16  and detector  18 . When an emergency event is detected by detector  18 , micro-controller  12  causes visual signal  14  to flash and audible signal  14  to emit sound bursts. 
     Visual signal  14  may be any suitable visual signal that can be used in a life safety system for visual annunciation of an emergency event. Preferably, visual signal  14  is a strobe light of the type described in the aforementioned Donati et al. patent. Audible signal  16  may be any suitable audible signal that can be used in a life safety system for audible annunciation of an emergency event. Preferably, audible signal  16  is an electronic horn. Detector  18  may be any suitable detector that detects an emergency event. For example, detector  18  may be a smoke detector. 
     Micro-controller  12  includes a microprocessor  20 , a memory  22 , a sound signal generator  24 , a flash pulse generator  26  and a flash charge circuit  27 . Memory  22  has stored therein a number of programs including an audible signal program  28 , a visual signal program  30  as well as a number of user entered modes  60 . Other programs also reside in memory  22 , such as those described in the aforementioned Donati et al. patent. 
     Microprocessor  20 , upon detection of an emergency event by detector  18 , operates under the control of audible signal program  28  to cause sound signal generator  24  to produce a sound signal D that is applied to audible signal  16 . Microprocessor  20  also responds to an emergency event detected by detector  18  to operate under the control of visual signal program  30  to cause flash pulse generator  26  to produce a flash pulse stream C that is applied to visual signal  14 . Visual signal program  30  also causes flash charging circuit  27  to produce a strobe charge signal B for storing energy in an energy storage device contained in visual signal  14 . 
     User entered modes  60  permit the user of the life safety system  10  to choose either a continuous sound mode  62  or a temporal sound mode  64 . In accordance with one aspect of the present invention, the user is given the option of choosing either a continuous flash mode  66  or a temporal flash mode  68 . This is a significant choice as the temporal flash mode consumes 25% less energy than the continuous flash mode during an emergency event annunciation. With less energy consumption, the size and cost of the power supply for life safety system  10  can be reduced. 
     In accordance with the present invention, visual signal program  30  includes an energy saver program  32 . Energy saver program  32  directs microprocessor  20  to operate visual signal  14  in the temporal visual mode or in the continuous visual mode. 
     Referring to FIG. 2, the waveforms begin at a time t 0  just after detector  18  detects an emergency event. Waveform A is a square wave that represents a standard international evacuation signal. It has a frequency in the range of about 0.33 to 3 Hz as selected by the user of life safety system  10 . Waveform B is the flash charge signal produced by flash charge circuit  27 . In one cycle, waveform B contains a sequence of charge pulses that serve to charge the energy storage device of visual signal  14 . 
     Waveform C is the flash pulse stream produced by flash pulse generator  26 . Waveform C is a repetitive temporal pattern that has four cycles with one flash pulse per cycle for the first three cycles and no pulse for the fourth cycle of the temporal pattern. For example, the time slice that begins with t 1  and ends with t 5  illustrates the temporal pattern. During the first three cycles from t 1  to t 4 , there is one flash pulse per cycle. During the fourth cycle from t 4  to t 5 , there is no pulse and no need to provide flash charge pulses to visual signal  14 . Visual signal  14  by time t 4  is already fully charged by the flash charge pulses provided during the third cycle from t 3  to t 4 . Accordingly, visual signal  14  and flash charge circuit consume 25% less energy than during a continuous mode in which there is one flash pulse per cycle. 
     Waveform D is the sound signal produced by sound signal generator  24 . Waveform D is shown for the temporal sound mode. Waveform C has a sequence of sound bursts that are controlled by microprocessor  20  to occur in unison with the flash pulses of waveform C so that audible signal  16  initiates a sound burst substantially simultaneously with visual signal  14  initiating a flash. 
     Referring to FIG. 3, energy saver program  32  begins at a step  34  with an inquiry as to whether an emergency event has been detected by, for example, detector  18 , and has not been cleared. If so, a step  36  determines if the temporal flash mode has been set. If so, a step  38  determines if the flash pulse count is less than 3. If so, a step  44  causes flash charge circuit  27  to send flash charge pulses to visual signal  14 . A step  46  keeps a count of charge pulses until the count is equal to a number n that represents the number of charge pulses needed to sufficiently charge visual signal  14 . A step  48  then enables flash pulse generator  26  to send a flash pulse to visual signal  14  and sound signal generator  24  to send a sound burst signal to audible signal  16 . A step  50  then causes the sound burst signal and the flash pulse signal to be sent simultaneously and in synchronization. This causes visual signal  14  to initiate a flash substantially simultaneously with audible signal  16  initiating a sound burst. 
     Assuming that the emergency event has not been cleared, steps  34  through  38  and  44  through  50  are repeated until step  38  determines that the flash pulse count is not less than three. When the flash count is equal to three, a step  40  resets the flash pulse count. A step  42  then causes a wait or delay of one cycle so that no pulse will be generated for this cycle. Steps  32  through  50  then continue until the emergency event has been cleared or visual program 30 times out the emergency event signaling process with a routine that forms no part of the present invention and, therefore, is not shown in FIG.  3 . 
     If the continuous flash mode  66  is set, steps  38  through  42  are skipped so that the steps  34 ,  36  and  44  through  50  are performed repetitively until the emergency event has been cleared or visual program  30  times out. 
     The present invention having been thus described with particular reference to the preferred forms thereof, it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the present invention as defined in the appended claims.