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is a string of lightweight "smart" fence posts (buoys) incorporating multiple embedded sensors in each post. A major feature of the fence is that it keeps small boats and other "nuisance" traffic well away from the high-value asset, simplifying the surveillance and security task. If the

Harbor Fence is breached in any way by surface craft, the embedded sensors transmit data to a laptop control con- sole and alarms are automatically generated. The system provides unattended waterside intrusion detection night or day in all weather conditions, and provides a map dis- play showing the location of the intrusion. Options include remote alarms, system operation over the inter- net, automatic camera pointing, and audible warnings on the fence posts themselves. "The Acoustic Fence (whether coupled with the Harbor Fence or other boom line) is essentially a tripwire - you can place it wherever you want to and change the shape as necessary," said

McDonald. "It's built in 120 foot sections for easy assem- bly and connection, and can be taken on ships for re- deployment in foreign harbors or deployed as a fixed sys- tem. "We designed the system to be set up and taken down from a small boat in an hour or so, depending on the length required," he said. "Once the system is turned on, it doesn't require an operator to watch over it. It sends out an alarm if it detects an intrusion, and if what it detects acts like a diver, it sends out an even higher level of alarm. The system does not require the high acoustic power needed by most diver sonar. This eliminates the

The harbor fence and the underwater sentry system protecting a ship in port.

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