Round Pin Plug Tops
BS546 is the British Standard number for old style round pin plug tops and sockets. They are used in older electrical installations or in special applications such as remotely switched lighting and stage lighting. 2A and 5A round pin plugs are type D and 15A are type M.
| Plug Rating | BS546 Type | Distance between centres of live / neutral pins |
| 2A / 2 Amp | Type D | 0.570 inches (14.5 mm) |
| 5A / 5 Amp | Type D | 0.750 inches (19.1 mm) |
| 15A / 15 Amp | Type M | 1.000 inch (25.4 mm) |
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