Abstract: A radio frequency tag for a radio frequency identification system is provided that includes an antenna and a receiver coupled to the antenna. The receiver receives and demodulates a message received on at least one frequency. A retransmit controller receives the message, determines a retransmit status for the message, and if the retransmit status is positive, initiates retransmission of the message for reception by another radio tag.

Abstract: A radio frequency tag for a radio frequency identification system is provided that includes an antenna and a receiver coupled to the antenna. The receiver receives and demodulates a message received on at least one frequency. A retransmit controller receives the message, determines a retransmit status for the message, and if the retransmit status is positive, initiates retransmission of the message for reception by another radio tag.

Abstract: A radio frequency tag for a radio frequency identification system is provided that includes an antenna and a receiver coupled to the antenna. The receiver receives and demodulates a message received on at least one frequency. A retransmit controller receives the message, determines a retransmit status for the message, and if the retransmit status is positive, initiates retransmission of the message for reception by another radio tag.

Abstract: A radio frequency tag for a radio frequency identification system is provided that includes an antenna and a receiver coupled to the antenna. The receiver receives and demodulates a message received on at least one frequency. A retransmit controller receives the message, determines a retransmit status for the message, and if the retransmit status is positive, initiates retransmission of the message for reception by another radio tag.

Abstract: A dual frequency radio tag for a radio frequency identification system is provided that includes an antenna system and a first receiver coupled to the antenna system. The first receiver receives and processes request signals from a first unit type at a first frequency. A second receiver is coupled to the antenna system and receives and processes request signals from a second unit type at a disparate second frequency. A transmitter is coupled to the antenna system and transmits response signals from the radio tag at the second frequency.

Abstract: A method and system for monitoring assets using radio frequency tags is provided that includes a plurality of primary tags. Each primary tag stores an identification of each linked tag associated with the primary tag. The primary tag receives a polling event and transmits a query message for linked tags within an operational range of the primary tag. Each linked tag receiving the query message transmits a response message that includes an identification of the linked tag. The primary tag receives the response messages and compares the identifications in the response messages to the identifications stored for each linked tag. Based on the comparison, the primary tag determines a monitored asset status.

Abstract: An access control system includes a plurality of door control systems each associated with an access door and including a relay control for operating the access door and a transmitter for eliciting a radio response from a tag at the access door. The response includes a tag ID and an access door ID. A receiver is operable to receive radio responses from tags at a plurality of access doors. An access door controller is coupled to the receiver and operable to receive the tag ID and the access door ID included in each radio response received by the receiver. The access controller determines whether access by the tag at the access door is authorized and controls the relay door to permit authorized access.

Abstract: A radio frequency tag accepts a received signal received by an antenna and demodulates that signal into a digital output using a comparator. The received signal is forwarded to a first comparator input. A threshold voltage generator generates a threshold voltage signal and forwards that signal to a second comparator input. The comparator compares the two inputs and generates a digital output based on the comparison.

Abstract: A data transmission system includes a reader transceiver and one or more tag transceivers. The reader transmits an activation signal to a tag. The tag selectively transmits a response signal to the reader at a specific time determined by a detected level of communications channel activity. The detector operates in a low-power standby state until the time it receives the activation signal, and then operates in an active state. The invention further incorporates a technique to maintain an extremely low power state to the tag during quiescent mode while retaining full sensitivity to reader activation signals. The reader transceivers are of a modular architecture with each module operating independently, yet in concert with the others. The modules are interconnected in a media independent method and can interact remotely with other modules.