| Number | Name | Date | Kind |
|---|---|---|---|
| 3109900 | Hook | Nov 1963 | |
| 3170050 | Buturuga | Feb 1965 | |
| 3233071 | Buzzell | Feb 1966 | |
| 3527914 | Spacek | Sep 1970 | |
| 4057794 | Grossfield | Nov 1977 | |
| 4496811 | Irwin | Jan 1985 | |
| 4820887 | Schmitz | Apr 1989 | |
| 5150913 | Hoelzl | Sep 1992 |
| Number | Date | Country |
|---|---|---|
| 2253263 | Jun 1975 | FRX |
| 0109563 | Apr 1925 | CHX |
| Entry |
|---|
| Nordy, "Switch Operation Protection", Aug. 1975, vol. 18, pp. 899-900 Patent Associated Literature (IBM Technical Disclosure Bulletin). |