| (subclass PureTwopole Twopole) | engineering.kif 498-498 | |
| (subclass IdealSwitch PureTwopole) | engineering.kif 501-501 | |
| (subclass IdealTwopole PureTwopole) | engineering.kif 506-506 | |
| (subclass Dissipator PureTwopole) | engineering.kif 509-509 | |
| (subclass AcrossVariableAccumulator PureTwopole) | engineering.kif 513-513 | |
| (subclass ThroughVariableAccumulator PureTwopole) | engineering.kif 517-517 | |
| (subclass Source PureTwopole) | engineering.kif 520-520 | |
| (subclass ElectricalTwopole PureTwopole) | engineering.kif 531-531 | |
| (subclass TranslatoryTwopole PureTwopole) | engineering.kif 569-569 |
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