Patents
Radio-frequency systems have the most manufacturers because they are not covered by patents, use well-known technology derived from radio communications, use little power, and can be manufactured without expensive metal alloys. There are exceptions however for example; a patented die-cut circuit manufacturing process is held by Miyake Inc. of Japan. Also, patents have recently been appearing for various combination tag designs for integration of both RF and RFID.
Until recently, acousto-magnetic systems were covered by now expired patents held by Sensormatic. WG Security Products, Inc. won a court battle against Sensormatic clarifying that WG Security Products acousto-magnetic systems did not infringe any Sensormatic patents. Disposable acousto-magnetic tags require special metal alloys; non-disposable ones require more expensive ferrite cores.
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