| Number | Name | Date | Kind |
|---|---|---|---|
| 3133170 | Nanninga | May 1964 | |
| 3331040 | Woodhead | Jul 1967 | |
| 3600528 | Leposavic | Aug 1971 | |
| 3742157 | Leposavic | Jun 1973 | |
| 3800104 | Lien et al. | Mar 1974 | |
| 3831118 | Bitko | Aug 1974 | |
| 3842230 | Kashio et al. | Oct 1974 |
| Entry |
|---|
| IBM Technical Disclosure Bulletin, H. L. Funk et al, "Keyboard Encoder," vol. 7, No. 11, Apr. 1965, pp. 1018, 1019. |