|
| US4652857 | 25. Juli 1986 | 24. März 1987 | | Method and apparatus for transmitting wide-bandwidth frequency signals from mines and other power restricted environments |
| US4864301 | 19. Okt. 1987 | 5. Sept. 1989 | Richard J. Helferich
Martin A. Schwartz | Variable speed transmission recording and retrieval of data |
| US4905003 | 24. Juli 1987 | 27. Febr. 1990 | Richard J. Helferich
Martin A. Schwartz | Analog/digital data storage system |
| US5003576 | 14. Apr. 1989 | 26. März 1991 | Richard J. Helferich
Martin A. Schwartz | Analog/digital voice storage cellular telephone |
| USRE34976 | 1. Febr. 1993 | 20. Juni 1995 | Richard J. Helferich
Martin A. Schwartz Revocable (Living) 1991 Trust | Analog/digital voice storage cellular telephone |
| USRE37618 | 11. Apr. 1997 | 2. Apr. 2002 | | Analog/digital data storage system |
