| Number | Date | Country | Kind |
|---|---|---|---|
| 74210700 | Dec 1985 | TWX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3489342 | Anderson | Jan 1970 | |
| 4311656 | Spriggs | Jan 1982 | |
| 4336948 | Couture | Jun 1982 | |
| 4342799 | Schwochert | Aug 1982 | |
| 4449839 | Bleuer | May 1984 | |
| 4500218 | Nishikawa | Feb 1985 |
| Entry |
|---|
| "Dummy Key Implementation", by Barker et al., IBM Technical Disclosure Bulletin, vol. 15, No. 6, Nov. 1972, pp. 1930-1931. |