Communications: electrical – Condition responsive indicating system – With particular system function
Reexamination Certificate
1999-05-14
2001-08-28
Pope, Daryl (Department: 2736)
Communications: electrical
Condition responsive indicating system
With particular system function
C340S315000, C340S534000, C340S537000, C340S538000, C340S315000
Reexamination Certificate
active
06281789
ABSTRACT:
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. In a system sold by Simplex Time Recorder Company disclosed in U.S. Pat. No. 4,796,025 (hereinafter the '025 patent), the contents of which are incorporated herein by reference, fire detectors are monitored and controlled through common power lines which also serve as communication links. Communications are by means of encoded pulses of voltage drops in power. Notification appliance circuits (NACs) may also be coupled to those communication links through a NAC controller but additional power is applied to the NACs due to the higher power requirements of NACs.
A number of notification appliances comprising audible alarms and strobes generally referred to as notification devices, are typically connected across common power lines on a notification circuit, either directly coupled to the central panel or through a NAC controller on a detector circuit. A first polarity DC voltage may be applied across the notification circuit in a supervisory mode of operation. In this supervisory mode, rectifiers at the notification appliances are reverse biased so that the alarms are not energized, but current flows through the power lines at the notification circuit to an end-of-line resistor and back, allowing the condition of those lines to 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.
U.S. Pat. No. 5,559,492 issued to Stewart el al. (hereinafter the '492 Stewart patent), the contents of which are incorporated herein by reference, further discloses that the visual alarms, or strobes, may be synchronized to fire simultaneously with power interruptions, also referred to as synchronization pulses, in the power lines. Additional timing lines for synchronizing the strobes are not required because the synchronizing signals are applied through the existing common power lines.
SUMMARY OF THE INVENTION
Extending full communications as disclosed in the '025 patent to NACs has drawbacks. For example, the signaling scheme inherently limits the amount of time that can be used to recharge the strobe between flashes. This is a significant detriment in alarm systems where the line voltage fluctuates widely due to load conditions and, consequently, more time is required to recharge the strobes to their respective firing voltage levels.
An alarm system of the present invention controls the operation of audible and visual alarm over common power lines and minimizes the time in which the line voltage is reduced to zero. A message is sent from a system controller to notification appliances having at least one audible alarm. The message includes a synchronization signal and a command signal embedded within the synchronization signal that controls the audible alarm. The notification appliance responds as directed by said command signal.
Preferably, the notification appliance includes a visual alarm that flashes upon receipt of the synchronization signal. The audible alarm responds to the command signal by turning off, turning on, or by generating a temporal or march time alarm.
In a preferred embodiment, the alarm system includes multiple notification appliances for signaling an alarm condition. The system controller intelligently controls the notification appliances including notification devices such as an audible or visual alarm through multi-bit digital messages sent over common communication lines. The alarm system has both a supervisory or standby and active mode of operation. In the standby mode, the notification appliances are powered at a first polarity DC voltage. In an active mode of operation, the first polarity voltage is reversed (or forward biased) to energize all the notification appliances on the communication lines. The system controller controls operation of the visual alarms by issuing synchronization signals, wherein the line voltage drops to zero, which trigger the visual alarms. An audible alarm command signal is embedded within the synchronization signal to control operation of the audible alarm.
The notification appliance includes a timer that controls operation of the audible alarm. In a preferred embodiment of the present invention, the timer is reset by the command signal which is intermittently embedded in the synchronization signal.
Preferably, the command signal is a series of negative voltage pulses and the synchronization signal is a drop-out in power supplied to the notification appliance. The command signal includes multi-bit voltage pulses extending from the drop-out.
According to yet further aspects of the present invention, an alarm system is provided having a system controller for generating a plurality of multi-bit messages that control at least one notification appliance that includes an audible alarm. A pair of communication lines connects the notification appliance to the system controller. The notification appliance includes an electronic circuit that receives a message comprising a synchronization signal and a command signal within the synchronization signal, wherein the command signal directs operation of the audible alarm.
Thus, the alarm system of the present invention controls operation of audible and visual alarms over common power lines while minimizing the time in which the line voltage is reduced to zero. This is accomplished by embedding a command signal, which controls the function of the audible alarms, in a synchronization signal used to control simultaneous actuation of the visible alarms. This allows extended charging time of the visual alarms between synchronization signals which is beneficial where the line voltage fluctuates due to load conditions thereby requiring more time to recharge the visual alarms to their respective firing voltage levels.
REFERENCES:
patent: 4262286 (1981-04-01), Tanigawa
patent: 4274084 (1981-06-01), Haus
patent: 4540890 (1985-09-01), Gangemi et al.
patent: 4555695 (1985-11-01), Machida et al.
patent: 4785195 (1988-11-01), Rochelle et al.
patent: 5400246 (1995-03-01), Wilson et al.
patent: 5525962 (1996-06-01), Tice
patent: 5559492 (1996-09-01), Stewart et al.
patent: 5598139 (1997-01-01), Karim et al.
patent: 5608375 (1997-03-01), Kosich
patent: 5751210 (1998-05-01), Kosich
Barrieau Mark P.
Capowski Anthony J.
Furtado Michael A.
Hamilton Brook Smith & Reynolds P.C.
Pope Daryl
Simplex Time Recorder Company
LandOfFree
Alarm system having improved control of notification... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Alarm system having improved control of notification..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Alarm system having improved control of notification... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2443135