The electrical outlet and power plug type A are widely used in Central America, Japan, Canada, and the USA.
The type A (NEMA 1-15) power plug is ungrounded and also works on socket type B.
The type A power plug is known as the NEMA 1-15 and was invented by Harvey Hubbell II in 1904.
The plug has two flat parallel pins, 1.5 mm thick and between 15.9 – 18.3 mm long. The ungrounded plugs are spaced 12.7 mm apart and are polarised.
They can be inserted in only one way due to the difference in the breadth of the plug’s blade.
The blade which is connected to the neutral has a width of 7.9 mm, while the hot blade width is 6.3 mm.
Though ungrounded type A plugs have been outlawed in America and Canada since 1965, type-A power outlets can still be found in old buildings.
One distinct feature of type A and B plugs is the presence of a hole close to each pin’s tip.
These holes fit into the bumps in contact wipers, thus ensuring a solid grip and attachment.
As a result, the plugs do not slip from the socket due to the plug’s or cord’s weight.
Certain sockets come without bump but with spring action blades, firmly attached to the plug once inserted into the socket.
In such instances, the plug’s holes have no function. In other instances, rods are slip between the holes, thus locking the cord in the socket.
This ensures that appliances such as vending machines do no get disconnected.