| Number | Date | Country | Kind |
|---|---|---|---|
| 62-136308 | May 1987 | JPX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3971916 | Moreno | Jul 1976 | |
| 4559418 | Imai | Dec 1985 | |
| 4641374 | Oyama | Feb 1987 | |
| 4760245 | Fukaya | Jul 1988 |
| Entry |
|---|
| The High Sensitivity Ceramic Microphone Incorporated with Multiple Poling System, Imai, Nobuomi (Primo Co., Ltd.) pp. 355-356 (Japanese Language Document). |