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Joined: Jul 2002
Posts: 103
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OK, here's a trivia question.
Why do male attachment plug prongs (some, not all) have round holes through them near the ends??? I DON'T know the answer!!
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Joined: Jul 2002
Posts: 680
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Joined: Sep 2001
Posts: 806
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Helps hold the plug into the receptacle. There is a corresponding "dimple" in the contact spring, which "locks" into the hole in the plug blade.
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Joined: Nov 2000
Posts: 2,236 Likes: 1
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And here I thought they were to clean the contacts...?
Makes sense though...
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI
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Joined: Aug 2001
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Don't forget that the holes also make it easy to wrap bare wires for Mexican-style extension cords.... ![[Linked Image]](https://www.electrical-contractor.net/ubb/biggrin.gif)
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Joined: Jul 2002
Posts: 103
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Interesting comments but:
The holes have been there a LONG time... long before lockout/tagout came on the scene, however I have seen some loto devices that use the holes.
The contact idea is interesting but I've never seen a receptacle with contact strips having dimples...
A cleaning function is interesting...could be!
Still searching!
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Anonymous
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I was told back in school that a long time ago receptacles had little spring loaded balls that would engage those holes.
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Joined: Mar 2002
Posts: 360
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My bet is that they are part of the manufacturing process, like maybe how they are hung onto when they mold the plug around them.
Trainwire
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Joined: Dec 2001
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I've got a 1970ies Sony stereo with NEMA plug and an unswitched outlet. When I push in a plug I can feel that the prongs get locked when fully inserted.
BTW, I was close to using the mexican style cord. I replaced a light switch in a room without a window, so I needed some temporary lighting. The only thing I could find was an imported US table lamp with an adaptor which has been hooked up forever in our living room. When I tried to hook it up I nearly got a fit. The adaptor was as stone aged as the lamp and it wouldn't fit Schuko receptacles! Finally I pulled two (illegal) ungrounded extension cords through the appartment and hooked my lamp up. SO much about being able to stick to codes...
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Joined: Jul 2006
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Don't forget that the holes also make it easy to wrap bare wires for Mexican-style extension cords.... I'm not an old timer on this site but I bet there are some pics of this in the violation photo forum. I've seen that practice done plenty of times, unfortunately. ![[Linked Image]](https://www.electrical-contractor.net/ubb/frown.gif) Luke
Luke Clarke
Electrical Planner for TVA.
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