Patent Document

BACKGROUND OF THE INVENTION 
     Typical building fire alarm systems include a number of fire detectors positioned throughout a building. Signals from those detectors are monitored by a system controller which, upon sensing an alarm condition, sounds audible alarms throughout the building. Flashing light strobes may also be positioned throughout the building to provide a visual alarm indication. A number of audible alarms and strobes, generally referred to as notification appliances, are typically connected across common power lines on a notification circuit. A first polarity DC voltage may be applied across the notification circuit in a supervisory mode of operation. In the supervisory mode, rectifiers at the notification appliances are reverse biased so that the alarms are not energized, but current flows through the power lines of the notification circuit to an end of line resistor and back so that the condition of those lines can be monitored. With an alarm condition, the polarity of the voltage applied across the power lines is reversed to energize all notification appliances on the notification circuit. 
     An alternate method of supervising audible alarms and strobes is to use addressable appliances as disclosed in U.S. Pat. Nos. 4,796,025 (Farley et al.); 5,155,468 (Stanley et al.); and 5,173,683 (Brighenti et al.). Each addressable appliance bas an individual address and is polled by the system controller to determine if it is present. When an appliance receives its associated address, its response to the poll indicates that the communication path between the appliance and the system controller is operational. 
     During installation of a building fire alarm system, the system controller is programmed to associate each fire detector input signal with one or more notification appliance circuits (in the case of non-addressable appliances) or individual notification appliances (in the case of addressable notification appliances). In a conventional system installation, programming can be verified by initiating an alarm input (e.g., smoke detector, pull station) to cause an alarm notification through the associated audible and visible notification appliances. A technician can then verify the programming by walking through the building and checking that the appropriate audible and visible notification appliances have been operated. Once the conventional building fire alarm system becomes operational, testing of individual notification appliances is accomplished by causing all of the appliances on a notification circuit to operate, followed again by a technician walking through the building to check that all of the appliances are functioning. 
     SUMMARY OF THE INVENTION 
     The conventional methods of verifying system installation and troubleshooting notification appliances can be very disruptive, especially in buildings such as hospitals which do not typically have an unoccupied period during which testing can be performed. 
     In accordance with the present invention, notification appliances connected to a system controller are provided, with each appliance having an alarm indicator such as an audible alarm or strobe, and a status indicator, such as an LED. The status indicator provides for system test modes that are not disruptive to building occupants. Accordingly, to test the programming of an alarm system, the system controller selects which notification appliances to operate in response to a test alarm input which is specific to one or more alarm condition detectors and communicates to each selected appliance an instruction to operate its associated status indicator without operating its associated alarm indicator. A technician can then check that the correct appliances have been operated, thus verifying the programming without disturbing the occupants of the building by activating the appliance. For notification appliances having both an audible alarm and a strobe, the status indicator can be operated at different rates to distinguish whether the audible alarm, strobe, or both would normally have been energized. 
     In a troubleshooting mode where there has been a supervision failure, the system controller selects to operate the status indicator of those notification appliances which respond to polling. This allows a technician to locate for troubleshooting purposes only those appliances having a nonoperating status indicator. 
     According to another aspect of the invention, an alarm system includes plural notification appliances that each have an alarm indicator, a microprocessor and a locally-activated switch. The microprocessor is programmed to transmit a first message in response to a manual activation of the switch. A system controller connected to the notification appliances receives the first message from the activated appliance and in response transmits a second message instructing the appliance to operate its associated alarm indicator for a test time interval. In a preferred embodiment, the locally-activated switch is a magnetic-field sensitive switch. In an alternate embodiment, the switch comprises an infrared sensor and switch circuitry. Each notification appliance further includes a status indicator which the microprocessor is programmed to operate in response to the switch activation for a second test time interval. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. 
         FIG. 1  illustrates an alarm system embodying the present invention. 
         FIG. 2  is an electrical schematic block diagram of an audible/visible alarm notification appliance in the system of FIG.  1 . 
         FIG. 2A  is a schematic block diagram of an alternate embodiment of an audible indicator circuit for the appliance of FIG.  2 . 
         FIG. 3  is a flowchart illustrating an installation verification process of the present invention. 
         FIG. 4  is a flowchart illustrating a troubleshooting process of the present invention. 
         FIG. 5  is a flowchart illustrating an individual appliance testing process of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A system embodying the present invention is illustrated in FIG.  1 . As in a conventional alarm system, the system includes one or more detector networks  12  having individual alarm condition detectors D which are monitored by a system controller  14 . When an alarm condition is sensed, the system controller signals the alarm to the appropriate devices through at least one network  16  of addressable alarm notification appliances A. Because the individual devices are addressable, supervision occurs by polling each device so that a network  16 , also referred to as a notification appliance circuit (NAC), can include one or more single-ended stub circuits  22 . As shown, all of the notification appliances are coupled across a pair of power lines  18  and  20  that also carry communications. 
     A preferred combination audible/visible notification appliance  24  is presented in FIG.  2 . Embodiments of individual audible and visible appliances are subsets of this schematic. Lines  18 ,  20  are coupled across over-voltage protector  110  to protect the appliance  24  against power surges and lightning strikes. A microprocessor  126  controls and operates audible indicator circuit  106 , flashing visible indicator circuit  108  and status indicator  120 . A shift register  118  provides the microprocessor  126  with serial access to six address bits set in DIP switch  112 , three device code bits set in register  116 , and a switch status bit set by switch  114 . Data-in and sync state inputs are provided to the microprocessor  126  through sync/data detector  122 . The microprocessor  126  includes data output line  138 , strobe power converter control line  140 , strobe flash trigger  142 , horn control line  144 , and LED control line  146 . The microprocessor  126  also includes random access memory (RAM)  129  and read only memory (ROM)  127 . In an alternate embodiment, the functions of microprocessor  126 , as disclosed hereinbelow are performed by an application specific integrated circuit (ASIC). 
     The audible indicator circuit  106  includes a drive circuit  134  that drives an audio transducer  136 . In the embodiment of  FIG. 2 , the audio transducer is a conventional piezo element. The microprocessor  126  operates the audible indicator circuit  106  by sweeping the drive circuit  134  with a nominal 3 kHz square wave signal on horn control line  144 . In an alternate embodiment (FIG.  2 A), the audible indicator circuit  106  can instead include a speaker  136 ′ as the audio transducer through which the microprocessor  126  plays prerecorded announcements retrieved from ROM  127 . In the alternate embodiment of appliance  24 , an audible indicator circuit  106 ′ includes a selector  137  which selects between the 3 kHz square wave signal on line  144  and an audio signal  135  under control of the microprocessor  126  on control line  143 . The audio signal  135  is provided to the appliance  24  from the system controller  14  either on a separate loop or superimposed on power/communication lines  18 ,  20 . 
     The flashing visible indicator circuit  108  can be easily constructed from the teachings in U.S. Pat. No. 5,559,492 (Stewart et al.), which is incorporated herein by reference in its entirety. The visible indicator circuit  108  includes a boost converter  128 , capacitor  131 , high-voltage trigger  130  and flash bulb  132 . The boost converter  128  is a charging circuit powered by the power lines  18 ,  20  that applies a series of current pulses to capacitor  131  on line  133  to charge the capacitor. The high-voltage trigger  130  is a firing circuit that causes the capacitor  131  to discharge through the flash bulb  132 . To avoid overcharging of the capacitor  131  as the flash bulb waits for a firing signal, the microprocessor  126  disables the boost converter  128  through control line  140  when the capacitor reaches a firing voltage level. In the alarm system disclosed in Stewart et al., the firing circuit responds to a change in voltage across the power lines to trigger the discharge. In the preferred embodiment of the notification appliance  24  of the present invention, the microprocessor triggers discharge through strobe flash trigger line  142 . 
     The status indicator  120  in the preferred embodiment is an LED that is controlled by the microprocessor  126  through control line  146 . While an unobtrusive LED indicator is preferred, it should be understood that in other embodiments the status indicator can include audible indicators such as a horn or speaker or even the circuit  106  operated at a much lower volume. 
     The switch  114  is a manually-activated switch, which is preferably a magnetic-field sensitive switch such as a reed switch. In a typical application, a technician manually passes a magnet across the face of the appliance to activate the reed switch. A single appliance test process using the switch is described further herein. 
     In an alternate embodiment, the switch  114  comprises an infrared receiver responsive to an activation signal from an infrared transmitter operated by the technician. A detected activation signal sets the switch status bit in shift register  118 . 
     The notification appliances  24  are operated through commands received over the NAC  16  from the system controller  14 . At system installation and at predetermined intervals, the appliances monitor the NAC  16  for a timing-training message broadcast from the system controller  14  which causes each appliance to adjust its local timebase to match that of the system controller  14 . 
     The alarm system has two normal modes of operation: SUPERVISORY mode and ALARM mode. In the SUPERVISORY mode, the system controller  14  applies 8 to 9 VDC to the NAC  16  to provide only enough power to support two-way communications between the system controller and the microprocessor  126  of each appliance  24 . In the ALARM mode, the system controller  14  applies a nominal 24 VDC to the NAC  16  to supply power to operate the audible and visible indicator circuits of the appliances. 
     In the preferred embodiment, the system controller  14  communicates digital data to the appliances using a three level voltage signal: sync (less than 3 volts), data  1  (8-9 volts) and data  0  (24 volts). Communication from the notification appliance  24  towards the system controller  14  is effected by the microprocessor  126  on data line  138 . 
     When not performing any functions, the microprocessor is put into a sleep mode to conserve power. The sync level signal is used to wake up the microprocessor  126  from a low power state. The appliance then checks whether a message is addressed to it and, if so, acts on the message. After a predetermined period with no activity, the device goes back to sleep. On reset or power up, the microprocessor  126  reads the DIP switch  112  to obtain the individual appliance address. It then monitors the NAC  16  for polls to this address by the system controller  14 . Device code bits hardcoded into register  116  indicate the appliance type, e.g., horn, flashing bulb or both. 
     An appliance can only act on a command by the system controller to turn on when the appliance is in ALARM MODE. An appliance  24  does not go into ALARM MODE operation until the voltage across the NAC  16  exceeds the minimum ALARM MODE voltage (e.g., 24 VDC) for more than 5 milliseconds, as determined by the microprocessor  126 . The appliance  24  turns off when the line voltage is determined to have dropped below the minimum ALARM MODE voltage continuously for greater than 5 milliseconds. 
     Selected groups of appliances  24  can be controlled by using group designators programmed by the system controller  14 . The appliance  24  retains the group designators in RAM  129  of the microprocessor  126 . In addition, default group designators include groups designated all audibles, all visibles, and all appliances. 
     Operation of the notification appliance  24  in accordance with the present invention will now be described with reference to  FIGS. 3-5 . 
     A flowchart illustrating an installation verification process of the present invention is shown in FIG.  3 . The notification appliances  24  are installed and the system controller is programmed during a system installation at step  100 . To test and verify the programming of the controller, a system test mode is entered at the system controller  14  at step  102  and a technician testing the system initiates an alarm input at a particular alarm condition detector (e.g., smoke detector, pull station) at step  104 . At step  106 , the alarm input is detected and the system controller selects one or more notification appliances to be operated that correspond to the specific detected alarm input at step  108 . In response, the system controller transmits an LED ON message to the selected notification appliances at step  110  to operate status indicator  120 . This then allows the technician to conduct a “silent test” of the appliances without actually sounding the audible indicators or flashing the visible indicators. After a test time interval, or on a command by the technician, the system controller transmits an LED OFF message to the selected appliances at step  112  to deactivate status indicator  120  and the alarm system returns to normal operation at step  114 . 
     In the case of a combination audible/visible notification appliance, there are alarm modes in which the flashing visible indicator, audible indicator or both are to be operated. Therefore, it is important when conducting silent testing of the appliances to provide an indication to distinguish such alarm modes. One method is to operate the status indicator  120  at a first rate to indicate that both the audible and visible indicators are being tested, at a second rate to indicate only the visible indicator, and at a third rate to indicate only the audible indicator. The different rates can instead be different on/off duty cycles. 
       FIG. 4  is a flowchart illustrating a troubleshooting process of the present invention. In the normal mode of operation, the system controller  14  supervises the notification appliance circuit  16  by polling the notification appliances  24  at step  200 . The appliances respond to the poll with an answer message transmitted back to the system controller at step  202 . If all of the appliances answer the poll at step  204 , then the system controller can assume that the appliances are functional and that the wiring has integrity. If an appliance does not answer the poll, a system trouble is issued by the system controller at step  206 . At step  208 , if the technician selects a diagnostic command, the system controller enters a troubleshooting mode on the specific NAC  16  associated with that particular appliance al  210 . The system controller at step  212  transmits an LED ON message to the ALL APPLIANCES group address on the specified NAC  16 . All of the appliances then operate their respective LED indicators, except for the faulty appliance, which can be visually identified by the technician. After a test interval long enough to allow proper identification of the faulty appliance or on a command by the technician, the system controller transmits an LED OFF message to the ALL APPLIANCES group address and the system returns to normal alarm operation at step  214 . 
     As noted in the background, conventional testing of a single notification appliance is accomplished by causing all of the appliances on a notification circuit to operate, followed by a technician walking through the building to check that all of the appliances are functioning. This process can be very disruptive in buildings such as hospitals which do not typically have an unoccupied period for such testing. A flowchart illustrating an individual appliance testing process in accordance with the present invention is shown in FIG.  5 . At step  300 , the system controller  14  sends a broadcast message to the appliances to put them into a manual test mode. In this manual test mode, the status of magnetic switch  114  is monitored by the microprocessor  126  at steps  302 ,  304 ,  306 ,  308 . At step  302  a timer is reset and the status of the magnetic switch bit is checked. If a switch activation has occurred, then at step  306  the timer is incremented and at step  308  the timer value is compared with a sample period. If the timer value is less than the sample period, the status checking loops through steps  304 ,  306 ,  308  until either a switch activation is not detected at step  304  or the timer value reaches the sample period at step  308 . In an alternate embodiment, the status checking loop  304 - 308  can be modified to only require the switch to be activated for a portion (e.g., 90%) of the sample period to account for “bounce” in the switch. 
     After the timer value reaches the sample period, meaning that the switch has been activated for the duration of the sample period and therefore a legitimate switch activation has occurred, the microprocessor  126  at step  310  operates the status indicator  120  briefly (e.g., 500 milliseconds) to serve as a local acknowledgment to the technician. The microprocessor then sends a SWITCH ACTIVE message to the system controller. The system controller receives the SWITCH ACTIVE message and may note the event in a system history log before putting the notification appliance circuit  16  into ALARM MODE and sending an APPLIANCE ON message to the particular activated appliance at step  312 . The microprocessor  126  receives the APPLIANCE ON message and operates the appropriate alarm indicator circuits  106 ,  108 . After a test interval, the system controller sends an APPLIANCE OFF message to turn off the alarm indicator circuits. 
     In an alternate embodiment, the individual appliance testing process is modified to aid the technician in determining which appliances have been tested and which are yet to be tested. Accordingly, at the commencement of manual test mode, the system controller  14  sends a broadcast LED ON-PERIOD message to cause the appliances to operate the status indicator  120  at a specified periodic rate. 
     Upon a switch activation as described above with respect to steps  304 ,  306 ,  308  of  FIG. 5 , the operation of the individual status indicator at step  310  is modified to instead deactivate the status indicator, followed by the remaining steps  312  and  314 . In this manner, a technician is able to distinguish untested appliances (blinking status indicator) from tested appliances (extinguished status indicator). Alternatively, the testing could begin with the status indicator off and each would be turned-on to indicate testing. 
     Equivalents 
     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various is changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described specifically herein. Such equivalents are intended to be encompassed in the scope of the claims.

Technology Category: 3