Patent ID: 7239238

Claim:
An electronic security seal comprising: a housing having a cavity; a cable locking device in the cavity; a cable having a hollow core and a first sealed free end and a second end, the second end being secured fixedly secured in the cavity, the first free end for selective insertion into engagement with the received locking device to lock the free end in the cavity; an electrical conductor in the cable hollow core, the conductor having a given resistance R, the conductor forming a loop within the cable and extending adjacent to the cable sealed first end, the loop terminating in a second free end with the conductor forming a pair of conductors extending beyond the cable at the cable second end and electrically connected to a first circuit; the first circuit located in the housing cavity including a signal generating circuit for generating a first signal manifesting a first cable locked state indicating that the cable free end is locked, the first circuit being responsive to a sensed tamper condition of the conductor for generating a second signal manifesting the sensed tampered condition of the locked cable; and a resistance measuring circuit for periodically measuring the resistance value of said electrical conductor loop, the first circuit being responsive to the measuring circuit for generating the second signal when the resistance value of the conductor loop differs from a predetermined reference value to provide a detected tamper condition; the first circuit including a power source having an output voltaae that decreases in value during a time period, the first circuit being arranged to correlate the predetermined reference resistance value of the conductor to at least one of a measured ambient temperature value and a measured decreasing power source output voltage value.