Electronic security seal

Abstract

A molded transparent thermoplastic housing has a programmable transmitting circuit for transmitting seal identifying serial number, seal location, container identification and other data to a local receiver. A door in the housing permits access to the circuit for programming the seal indicia and related data for transmission. A contact arrangement forms a switch upon insertion of a locking bolt into a locking mechanism in the housing and applies battery power through the bolt to activate the data generating circuit. A conductor along the bolt shank is connected to the circuit provides a tamper evident signal to the circuit when the bolt is severed. The circuit senses the removal of the bolt or severed bolt condition for generating a “tamper” signal which is transmitted to a local receiver/reader. The conductor at the bolt may be a wire in a plastic tube surrounding the shank, a conductive layer over an insulation layer on the shank and over the conductive bolt head in ohmic contact with the head or a wire in a hollow metal tube. Severing the bolt severs the wire or the ohmic contact between the head and coating or between the head and the wire in the tube to indicate tampering. The seal periodically in random periods transmits the seal condition, whether normal or tampered. In an alternative embodiment, an interrogation unit may interrogate the seal which then transmits its locked or tampered states according to the locked or tampered condition of the bolt.