Patent ID: 7436304

Claim:
A method for use with an electrically conductive line and with tags, the line having first and second ends and being at least twenty feet in length, the tags each having a respective identifier and disposed to receive queries at a radio frequency no greater than 1 MHz and to emit responses thereto at a radio frequency no greater than 1 MHz, the tags each mechanically affixed to a respective bag having an opening and a closure for the opening, the method comprising the steps of: defining a first scene of interest having a perimeter, the scene of interest having an area, the area exceeding twenty-five square feet, the perimeter extending at least twenty feet; deploying the line starting with its first end at a first point at the perimeter, along the perimeter around the first scene of interest, and returning with its second end to the first point; connecting the first and second ends to a first apparatus operating at a radio frequency no greater than 1 MHz; operating said apparatus to emit a query; operating said apparatus to listen for a response to the query from a tag; in the event of a response, extracting an identifier from the response, storing the identifier in said apparatus, and transmitting a silence request with respect to the identifier; repeating the emitting, listening, extracting, storing, and transmitting steps, thereby accumulating a list of identifiers; recording times at which the list changes, thereby detecting events of tags entering and leaving the first scene of interest; after the preceding steps, removing the line; after removing the line, defining a second scene of interest having a perimeter, the second scene of interest having an area, the area exceeding twenty-five square feet, the perimeter extending at least twenty feet; deploying the line starting with its first end at a first point at the perimeter, along the perimeter around the second scene of interest, and returning with its second end to the first point; and connecting the first and second ends to said first apparatus operating at a radio frequency no greater than 1 MHz.