| Number | Date | Country | Kind |
|---|---|---|---|
| 3-328721 | Dec 1991 | JPX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4203130 | Doumit et al. | May 1980 | |
| 4817075 | Kikuchi et al. | Mar 1989 |
| Entry |
|---|
| Nihon Keizai Shinbun, Mar. 15, 1992 (with Partial Translation). |
| IEEE Global Telecommunications Congerence & Exhibitions, Conference Record vol. 1 of 3, Dec. 2-5, 1990. |