| Number | Name | Date | Kind |
|---|---|---|---|
| D206590 | Haggstrom et al. | Jan 1967 | |
| D301455 | Hotsumi et al. | Jun 1989 | |
| D324370 | Lay et al. | Mar 1992 | |
| D328889 | Seki | Aug 1992 |
| Entry |
|---|
| Motorola Marketing Brochure, R3, Sec. 5, Item 146, "Keynote Tone and Voice Pager Two-Tone Sequential Coding", 1989. |
| NEC chargers in NEC publication Cat. No. E44116 881220503KM. |