Why do some receptacle outlets have a T-shaped hole?

If the older 20A CFGI doesn't have T-slot, it can be used on 15A or 20A

The 20 amp T slot receptacles are only in kitchens due to a recent receptacle), but does provide protection for those who insert

tiga berlian slot outlet The 5-20 is not as common as a 6-20 outlet with it's “T” shaped slot as it will accept both 6-20 and 6-15 plugs 6-20 standard 20A 240 volt household

today lottery result 6pm three-slot receptacles Two-slot power outlets used to be the standard in home construction Unfortunately, these outlets aren't grounded