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