Yeah, that's my issue with wanting to know the reason behind that.
Some 110-volt 20-amp receptacles don't have the T slot.
They won't accept standard 15 amp plugs.
Sorry, I guess I didn't make that clear in my response to the initial poster. XD
120 volt/20-amp receptacle (marked as Non-NEMA in the P&S website)
[This message has been edited by SvenNYC (edited 05-27-2005).]