Type A - NEMA US/Japanese 2-pin

Flat blade attachment plug

 

 

Flat blade plug

Where found:

American Samoa, Anguilla, Antigua, Aruba, Bahamas, Bangladesh, Barbados, Bermuda, Bolivia, Brazil, Cambodia, Canada, Cayman Islands, China (without holes in blades and slightly shorter blades), Colombia, Costa Rica, Cuba, Ecuador, El Salvador, Guam, Guatemala, Guyana, Haiti, Honduras, Jamaica, Japan, Laos, Lebanon, Liberia, Maldives, Mexico, Micronesia, Montserrat, Netherlands Antilles, Nicaragua, Niger, Okinawa, Panama, Peru, Philippines, Puerto Rico, St. Vincent, Saudi Arabia, Tahiti, Taiwan, Thailand, United States, Venezuela, Vietnam, Virgin Islands (U.S.& British), Yemen.

Commentary:

This plug and receptacle are technically known as NEMA 1-15 (North American 15 A/125 V ungrounded).
Standardized by the U.S. National Electrical Manufacturers Association[7] and adopted by 38 other countries, this simple plug with two flat parallel pins, or blades, is used in most of North America and on the east coast of South America on devices not requiring a ground connection, such as lamps and "double-insulated" small appliances. NEMA 1-15 sockets have been prohibited in new construction in the United States and Canada since 1962, but remain in many older homes and are still sold for replacement use only. Type A plugs are still very common because they are compatible with type B sockets.

Early designs could be inserted either way, but some modern plugs make the neutral blade wider than the live blade; so that a polarized plug can be inserted only one way. New polarized plugs will not fit in old type A sockets, but both old and new type A plugs will fit in new type A and type B sockets.

A similar plug and receptacle commonly foundin Japan is technically known as JIS C 8303, Class II (Japanese 15 A/100 V ungrounded).

The Japanese plug and socket are identical to NEMA 1-15. However, the Japanese system incorporates stricter dimensional requirements for the plug housing, different marking requirements, and mandatory testing and approval by Japanese standards agencies.

Some older Japanese outlets and multiplug adapters are non-polarized -- the slots in the sockets are the same size - and will only accept non-polarized plugs. Japanese plugs should be able to fit into modern North American outlets without trouble, but North American appliances with polarized plugs may require adapters or replacement non-polarized plugs to connect to older Japanese outlets; or even replacement of the wall socket itself.

Type B - North American 3-pin

 

Flat blades with round grounding pin

Type B plug and receptacle

Where found:

All of the above noted for Type A except Bangladesh, Bolivia, Cambodia, China, Dominican Republic, Korea, Liberia, Maldives, Peru, St. Vincent, Tahiti, Thailand, Vietnam, Yemen.
Also found in Azores, Belize, Trinidad and Tobago.

Commentary:

This plug and receptacle are technically known as NEMA 5-15 (North American 15 A/125 V grounded)

The type B plug has two flat parallel blades like type A, but has a round ground or earth pin. It is rated for 15 amperes at 125 volts. The ground pin is longer than the live and neutral blades, so the device is grounded before the power is connected. The neutral blade in the Type B socket is wider than the live one to prevent polarized Type A plugs being inserted incorrectly. Type B plugs often have both pins narrow since the ground pin enforces polarity.

Looking directly at a type B outlet with the ground at the bottom, the neutral slot is on the left, and the live slot is on the right. They may be installed with the ground at the top or on either side. In new residential construction since about 1992, a 20-amp receptacle with a T-slot for the neutral blade allows either 15-ampere parallel blade plugs or 20-ampere plugs to be used.

Japan also uses a Type B plug similar to the North American one.  However, it is less common than its Type A equivalent.