Vehicle detector with power failure information saving
First Claim
1. In a vehicle detector having circuitry powered by a source of electrical power for sensing changes in an associated inductive loop related to the presence of a vehicle in the vicinity of the loop and for generating a Call signal in response to such changes;
- the improvement comprising a non-volatile memory device for receiving and storing reference information from the vehicle detector, a power monitor circuit for detecting an impending loss of power to the vehicle detector, and means responsive to said power monitor circuit for storing said reference information in said non-volatile memory device upon detection of an impending loss of power.
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Accused Products
Abstract
A method and apparatus for storing reference information in a non-volatile memory unit when a power loss to a vehicle detector is imminent. A power monitor circuit senses an impending power loss. In response, the vehicle detector transfers reference information, including a reference count and the number of loop cycles over which the reference count was accumulated, as well as optional detector status information, from the vehicle detector volatile memory (typically RAM) to the non-volatile memory unit. When power is resumed, the information stored in the non-volatile memory unit is restored to the vehicle detector. The restored information prevents improper and potentially dangerous vehicle detector operation caused by the loss of reference information during unpredictable power losses. The transfer operation is not performed if the power loss is due to a mechanical disconnection of power. By limiting the information transfer operation to only an impending power loss condition, the use of non-volatile memory to store the information is made practically feasible.
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Citations
20 Claims
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1. In a vehicle detector having circuitry powered by a source of electrical power for sensing changes in an associated inductive loop related to the presence of a vehicle in the vicinity of the loop and for generating a Call signal in response to such changes;
- the improvement comprising a non-volatile memory device for receiving and storing reference information from the vehicle detector, a power monitor circuit for detecting an impending loss of power to the vehicle detector, and means responsive to said power monitor circuit for storing said reference information in said non-volatile memory device upon detection of an impending loss of power.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of saving reference information in a vehicle detector volatile memory prior to an impending power loss, said method comprising the steps of:
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(a) sensing an impending loss of power to the vehicle detector; and
(b) storing the reference information in a non-volatile memory device before the vehicle detector becomes inoperative due to a loss of power. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification