| Number | Date | Country | Kind |
|---|---|---|---|
| 2121451 | Apr 1994 | CAX |
| Number | Name | Date | Kind |
|---|---|---|---|
| 1466361 | Getchell | Aug 1923 | |
| 2273487 | Heyman | Feb 1942 | |
| 2874980 | Browning | Feb 1959 | |
| 2894534 | Kennedy | Jul 1959 | |
| 3240869 | Jureit | Mar 1966 | |
| 4924646 | Marquardt | May 1990 | |
| 5280138 | Preston et al. | Jan 1994 | |
| 5488198 | Kramer | Jan 1996 |
| Number | Date | Country |
|---|---|---|
| 2097969 | Dec 1993 | CAX |
| Entry |
|---|
| IBM Technical Disclosure Bulletin, vol. 3, No. 6 Nov. 1960. |