Fire alarm system
First Claim
1. A fire alarm system having a plurality of fire detectors connected in parallel with each other to signal lines leading to a central signal station for detecting a change in the ambient physical phenomena caused by a fire and responding to the station with the detection signal, which system is characterized in thatsaid signal lines connecting to the respective fire detectors are also used as power lines;
- each of said fire detectors receives calling clock pulses superposed on a power supply voltage and transmitted from the central signal station through the power/signal lines and returns the detection signal in the mode of current to the signal station; and
said central signal station comprises;
a calling control means which outputs the calling clock pulses by transmitting one calling clock pulse to one fire detector and providing, between the calling clock pulses, a time for detecting at least a steady-state current and a time for detecting the detection signal current;
a current detecting means for detecting the steady-state current and the detection signal current;
a computing means for obtaining a difference between the steady-state current and the detection signal current; and
an alarm means for giving an alarm upon determination of a fire based on the output value from the computing means.
1 Assignment
0 Petitions
Accused Products
Abstract
A fire alarm system having a plurality of fire detectors connected in parallel with each other to a pair of power/signal lines leading to a central signal station and adapted to respond to the signal station with a detection signal in the mode of current and controlling the signalling between the fire detectors and the signal station. The detection of a fire is accomplished by computing a difference between a steady-state current flowing through the signal lines and a detection current which are detected in an analog amounts. Each of the fire detectors is called by a simple calling clock pulse whose transmitting timing is controlled by a microcomputer of the central signal station to transmit a detection data. The generation timing of the calling clock pulses is freely selectable to effect a desired control of the fire detectors.
-
Citations
10 Claims
-
1. A fire alarm system having a plurality of fire detectors connected in parallel with each other to signal lines leading to a central signal station for detecting a change in the ambient physical phenomena caused by a fire and responding to the station with the detection signal, which system is characterized in that
said signal lines connecting to the respective fire detectors are also used as power lines; -
each of said fire detectors receives calling clock pulses superposed on a power supply voltage and transmitted from the central signal station through the power/signal lines and returns the detection signal in the mode of current to the signal station; and said central signal station comprises; a calling control means which outputs the calling clock pulses by transmitting one calling clock pulse to one fire detector and providing, between the calling clock pulses, a time for detecting at least a steady-state current and a time for detecting the detection signal current; a current detecting means for detecting the steady-state current and the detection signal current; a computing means for obtaining a difference between the steady-state current and the detection signal current; and an alarm means for giving an alarm upon determination of a fire based on the output value from the computing means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
Specification