| Number | Name | Date | Kind |
|---|---|---|---|
| 3126242 | Herman | Mar 1964 | |
| 4372638 | Sohler | Feb 1983 | |
| 4830631 | Hsueh | May 1989 | |
| 4884050 | Kozel | Nov 1989 | |
| 4941851 | Hsueh | Jul 1990 | |
| 4943248 | Colleran et al. | Jul 1990 | |
| 4986767 | Kozel | Jan 1991 | |
| 5324214 | De Castro | Jun 1994 | |
| 5476396 | De Castro | Dec 1995 |
| Number | Date | Country |
|---|---|---|
| WO 9605990 | Feb 1996 | WOX |
| Entry |
|---|
| 1994 -Sound Quest, Inc. -Catalog p. 52. |
| 1996 -Magnadyne -Catalog p. 33. |