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| US4166236 | 24 jan 1977 | 28 aug 1979 | | Electric energy saving three-position combination switching device |
| US4259619 | 16 maj 1977 | 31 mar 1981 | Power Controls Corporation | Three-way light dimmer switch |
| US4549116 | 26 jun 1981 | 22 okt 1985 | | Electric energy saving two-position combination switching device |
