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. Note;[1] 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.