Puede estar bajo cualquier de los siguientes patentes de Estados Unidos:
4,797,916
5,426,690
5,650,790
5,660,269
5,754,407
5,758,289
5,893,034
5,912,968
6,070,082
6,125,277
6,782,098
6,788,920
6,953,118
7,023176
Otras patentes pendientes.
5,434,905
5,491,745
5,661,780
5,663,981
5,768,345
5,787,356
5,915,227
5,929,598
6,253,088
6,314,278
6,788,953
6,839,550
82
5,493,605
5,533,010
5,671,248
5,696,471
5,794,152
5,801,466
5,930,720
5,960,358
6,418,209
6,618,015
6,889,184
6,901,271
5,574,727
5,581,598
5,717,312
5,732,355
5,825,161
5,864,619
5,987,330
6,044,281
6,671,315
6,714,630
6,907,094
6,914,940