Time calibration method for security system using sensors

• US 7,024,325 B2
• Filed: 11/07/2002
• Issued: 04/04/2006
• Est. Priority Date: 11/09/2001
• Status: Active Grant

• Current Assignee: Nihondensikougaku Company Limited
• Original Assignee: Nihondensikougaku Company Limited
• Inventors: Orita, Takehiro, Orita, Kouji, Kuriuchi, Kimito
• Primary Examiner(s): Bui, Bryan
• Application Number:
  US10/289,396
• Publication Number:
  US 20030105602A1
• Time in Patent Office: 1,244 Days
• Field of Search: 702/89, 702/85, 702/116, 700/9, 700/276, 340/426.19, 340/506, 340/508
• US Class Current: 702/89
• CPC Class Codes: G08B 25/10 using wireless transmission systems G08B25/009 takes precedence

Abstract

Among multiple surveillance devices for mechanical security monitoring provided in a security system using sensors at least one of the multiple surveillance devices is equipped with a receiver for receiving standard time data and the standard time data received by the receiver is sent over a distribution line to required surveillance devices not equipped with receivers. This enables highly accurate time calibration among the multiple surveillance devices for mechanical security monitoring to be efficiently achieved using a power-line carrier (PLC) technology and, as such, allows sharing of accurate time data among the surveillance devices.

Claims

1. A time calibration method for a security system using sensors that enables time calibration of clocks of multiple surveillance devices used by the security system to identify the time of occurrence of a sensed event, the method comprising:

a step of receiving standard time data from a time source external to said security system in at least one of the multiple surveillance devices of the security system;

a step of sending the standard time data received over a distribution line to other surveillance devices for calibrating each clock in said surveillance devices; and

a step of storing output data from a sensor with a calibrated time clock signal.

2. A time calibration method as claimed in claim 1, wherein each of said surveillance devices has a power-line carrier transceiver and the standard time data is sent through the power-line carrier transceiver to the other surveillance devices.

3. A time calibration method as claimed in claim 1, wherein in the surveillance device the time data and an output data from the corresponding sensors are stored in a memory.

4. A time calibration method as claimed in claim 1, wherein a time calibration is performed by overwriting the time data of the clock with the standard time data.

5. A time calibration method as claimed in claim 2, wherein in the surveillance device the time data and an output data from the corresponding sensors are stored in a memory.

6. A time calibration method as claimed in claim 2, wherein a time calibration is performed by overwriting the time data of the clock with the standard time data.

7. The time calibration method of claim 1, wherein said standard time data is transmitted from a national standard clock to said at least one surveillance device.