| 335 / | HD | ELECTRICITY: MAGNETICALLY OPERATED SWITCHES, MAGNETS, AND ELECTROMAGNETS | 
| 209 | DF | MAGNETS AND ELECTROMAGNETS {10} | 
| 220 | DF | .~ With magneto-mechanical motive device (e.g., electromagnet with armature) {21} | 
| 239 | DF | .~.~ With time delay armature-movement control means {3} | 
| 240 |  | .~.~.~ Dashpot type |