Tags are small and inexpensive devices which may be attached to or put in objects, persons, vehicles, and aircraft. The tags may periodically transmit their identification code (ID), status, data and other information, and may also receive information, such as coordinate, setup, programming, control and/or other information. Active tags, operating on a commodity battery, are capable of several hundred feet of radial coverage. Hundreds or thousands of tags can be simultaneously detected and read.
In many applications, there is a need for a tag to have additional capabilities, such as providing tamper sensors and other inputs that are integrated with the tag. Specifically, there is a need for tags that can provide security for items, objects, material, vehicles or persons, in such a manner as to prevent entry, theft, sabotage or other detrimental activity. The tag may seal, or otherwise secure, items it is designed to protect but also to protect itself from being overcome or rendered ineffective.
Additionally, there is the need for a tag with communication capabilities and functions so that it can play a part in global monitoring, supply chain management and security management, with remote monitoring, control and processing capability, such as on an Internet website. In one example, a tamper tag employs a closed-loop fiber optic cable, where both ends of the cable are connected to the tag, and the cable is fed through, around or is attached to one or more items such as containers containing a critical or dangerous material. A light or infrared signal originating in the tag is fed to one end of the cable and detected at the other end by the same tag. Any attempt to disconnect, cut or remove the cable, is immediately detected and a tamper-initiated wireless signal, such as a radio signal, is sent to one or more receivers and a monitoring system.
In another example, it may be desired to globally monitor and track the movement of containers, mail, packages or other items, using the Internet, wireless networks, telephone lines and other communication means. The monitoring and tracking can be accomplished with signposts and local controller systems located in a ship, train, airplane, truck loading and unloading port and customs area. Signposts can interrogate a tamper tag on a container, sending a signpost ID, location, time and date stamp, and other status information that can be transmitted to a remote overall system controller, and/or stored in the tag in order to maintain a trip and incidence record, for reading upon arrival at a final destination. The tamper tag can also seal or secure the container and send an immediate alert signal if the container or tag integrity is being tampered with or if it has been tampered with in the past.
Conventional tag systems employ a wire or conductive cable, and measure the continuity of a voltage or current to confirm that tampering has not occurred. However, one can place a bypass connection, and then cut the wire with the system not detecting a tamper event. In a more complex case, a cable with an internal conductor and external connector is used, requiring that both connections be bypassed.
Other prior systems use an intermixing of fibers in a fiber optic bundle or cable so as to create a unique “fingerprint” of the output pattern. Fiber optics are highly advantageous since they provide high immunity to environment inputs such as moisture and electrical interference, do not create a conductive path, and do not require two conductors to create a circuit. However, prior systems are complex and costly because they require multiple receiving detectors, apertures, and lenses to read the optic pattern.
Other fiber optics systems use a visual light or infrared signal that is operated by a random number sequence. However, the number of alternatives is neither very high nor very random, because it is very difficult to create a high number of codes in a small tag. As a result, the “random” number can be easily analyzed and replicated, and a pattern can be ascertained and duplicated, to defeat the system.
Examples of conventional signpost, tag and receiver monitoring, tracking and locating systems include the following:
U.S. Pat. No. 6,420,971 discloses an electronic seal that has a housing and a closure member operable with the housing to form a seal. The electronic seal has a core and a sensor assembly for detecting tampering. The core is a fiber optic cable, and the sensor assembly includes an integrity sensor having an optical source and an optical detector.
U.S. Pat. No. 6,624,760 discloses a low-cost monitoring system that has an extremely low power consumption which allows remote operation of an electronic sensor platform (ESP) for a long period. The monitoring system provides authenticated message traffic over a wireless network and utilizes state-of-health and tamper sensors to ensure that the ESP is secure and undamaged. The system has a robust ESP housing suitable for use in radiation environments. With one base station (a host computer and an interrogator transceiver), multiple ESP's can be controlled at a single monitoring site.
U.S. Pat. No. 5,646,592 discloses a simple trip-wire or magnetic circuit for a shipping container. The trip-wire or magnetic circuit provides continuity, which is detected electrically. If the continuity is interrupted by a forced entry of the container, electrical detection means, such as a radio-frequency-identification (RFID) tag, will alert a monitoring station. Also a magnetic circuit and a detection device (RFID tag) can be embedded into a shipping article during manufacturing. The RFID tag would communicate with an interrogator unit, which can be connected to a host computer. The interrogator and/or the host computer would then monitor the shipping container's status (opened or closed).
U.S. Pat. No. 4,523,186 discloses a seal system for materials, which indicates changes in environmental conditions that evidence attempts to bypass the seal. The seal system includes a detector for reading an optical signal transmitted through a loop, and one or more additional detectors for detecting environmental changes. These detectors are operatively associated with the seal so that detection of a break in the optical signal or detection of environmental changes will cause an observable change in the seal.
In U.S. Pat. No. 4,447,123, a fiber optic seal includes a transparent seal body having two spaced apart cavities. The ends of a fiber optic cable are secured within the spaced apart cavities, respectively. An electronic verifier injects light into one of the cable ends via a plurality of illumination light guides fixed within the seal body between an external surface and the illumination cavity. Light emitted from the other end of the fiber optic cable is transmitted from the detection cavity to the exterior surface of the sealed body via a plurality of detection light guides. The light is measured and converted by the verifier to provide a seal signature.
These conventional tamper monitoring systems have several drawbacks. For example, the conventional systems measure the presence or absence of a simple or constant signal in a cable. This makes the system easy to tamper with, because the signal can be easily duplicated and the cable can be easily bypassed.