| 摘要 |
A system is provided for detecting wind shifts on a floating vessel which is anchored. The system has particular applicability to commercial gill net fishing where a net is set for the night and a fishing boat is tied to the downwind end of the net. The system employs a modified compass which has a compass rose freely rotatable relative to and in electrical isolation from a housing. An electrical contact is mounted on the compass rose and is electrically connected to a power supply and to an alarm. The power supply is also connected to limit contacts on the housing. The limit contacts are initially oriented to locations on opposite sides of the electrical contact on the compact rose when the vessel is anchored to the downwind end of the net to define allowable variations in wind direction. A significant wind shift will reorient the vessel relative to the net to maintain the vessel at a location downwind from its anchoring point on the net. The compass rose remains pointed north while the vessel and the compass housing are rotated about the anchoring point on the net and relative to the compass rose in response to wind shifts. The rotation of the compass housing relative to the compass rose establishes electrical connection through the electrical contact on the compass rose and at least one of the limit contacts, thereby activating an alarm to alert the crew to a wind shift beyond the allowable variations in wind direction.
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