Radio alarm system
First Claim
1. A radio alarm system comprising a plurality of terminal devices each of which is connected to a detector for detecting any abnormal state and each of which is adapted to transmit information in the form of a radio signal based on a detection signal from said detector, and a central unit adapted to receive and decode the radio signal from said terminal device and to give an alarm;
- each of said terminal devices comprising;
channel searching means adapted to perform, when transmitting information, carrier sensing successively on a plurality of transmission channels previously allocated thereto, in a predetermined sequence and over a preset delay time, thereby selecting a free channel which is not being used by any other terminal device; and
transmission control means adapted to transmit said information, along with the terminal device address, in a continuous manner to said central unit through the channel selected by said channel searching means, by repeating a cycle of a predetermined transmission period and a predetermined rest period.
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Accused Products
Abstract
A radio alarm system for detecting abnormalities such as a fire having a central unit which is adapted to receive and decode the radio signal transmitted from each terminal device and to give an alarm and a plurality of terminal devices which is connected to a detector for detecting an abnormal state and is adapted to transmit information in the form of a radio signal based on an abnormality detection signal from the respective associated detector. And delay times which vary from terminal device to terminal device are set, and the selection of a free channel for transmission is effected in each terminal device by performing carrier sensing over a delay time peculiar to that terminal device. Each of the terminal devices is equipped with a channel setting means which successively performs, when transmitting information, carrier sensing on a plurality of transmission channels previously allocated the terminal device, in a previously determined order, thereby selecting a free channel which is not being used by an other terminal device.
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Citations
7 Claims
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1. A radio alarm system comprising a plurality of terminal devices each of which is connected to a detector for detecting any abnormal state and each of which is adapted to transmit information in the form of a radio signal based on a detection signal from said detector, and a central unit adapted to receive and decode the radio signal from said terminal device and to give an alarm;
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each of said terminal devices comprising; channel searching means adapted to perform, when transmitting information, carrier sensing successively on a plurality of transmission channels previously allocated thereto, in a predetermined sequence and over a preset delay time, thereby selecting a free channel which is not being used by any other terminal device; and transmission control means adapted to transmit said information, along with the terminal device address, in a continuous manner to said central unit through the channel selected by said channel searching means, by repeating a cycle of a predetermined transmission period and a predetermined rest period. - View Dependent Claims (2, 3, 4, 5)
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6. A radio alarm system comprising a plurality of terminal devices each of which is connected to a detector for detecting any abnormal state and each of which is adapted to transmit information in the form of a radio signal based on a detection signal from said detector, and a central unit adapted to receive and decode the radio signal from said terminal device and to give an alarm;
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each of said terminal devices comprising; channel searching means adapted to set the terminal device in a receiving state first when any abnormality is detected and to perform carrier sensing with a reception signal obtained through an oscillation generated by setting, in a PLL circuit, dividing ratio data on a local oscillation frequency, thereby selecting a free channel which is not being used by any other terminal device; and transmission control means adapted to generate an oscillation by setting, in said PLL circuit, dividing ratio data on the carrier frequency of the selected free channel so as to transmit an abnormality detection signal to said central unit; said central unit successively performing carrier sensing on the same predetermined number of channels as are allocated to each of said terminal devices and fixing the carrier channel where any carrier is detected in a receiving state so as to receive the abnormality detection signal. - View Dependent Claims (7)
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Specification