Applications
There are four ratings of plug and socket in BS 546, (2 amperes, 5A, 15A and 30A). Each has the same general appearance but they are different physical sizes to prevent interchangeability. Fused plugs have been optional since the original BS 546:1934 with maximum fuse ratings of 2A in the 2A plug, and 5A in the 5A, 15A and 30A plugs.
The 15 Amp(A) sockets were generally given a dedicated 15 A circuit. Mulitiple 5 A sockets might be on a 15 A circuit, or on a dedicated 5 A circuit. Lighting circuits fused at 5 A were generally used to feed the 2 A sockets. Adaptors were available from 15 A down to 5 A and from 5 A down to 2 A so in practice it was possible for an appliance with the smallest size of flex to be protected only by a 15 A fuse. This is a similar level of protection to that seen for portable appliances in other countries, but less than the protection offered by the BS 1363 fused plug.
In theory, 15 A plugs were to be used for large appliances such as electric heaters, while small appliances such as radios or table lamps were supposed to use 5 A. In practice this was inconvenient, and in many households the 15 amp plug was used for everything. Adaptors were available which allowed 2 or 5 amp plugs to be used in 15 amp sockets.
The larger top pin is the earth connection, the left hand pin is neutral and the right hand pin as line when looking at a socket or at the rear of a plug.
The 2 A, 5 A, and 15 A, connectors of BS 546 are duplicated by Group B1 of the GOST 7396 standard.
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