8,(Type D)and (Type M)
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BS 546 and related types

BS 546 3-pin plugs. Left to right: 15 A, 5 A and 2 A.

BS 546, “Two-pole and earthing-pin plugs, socket-outlets and socket-outlet adaptors for AC (50-60 Hz) circuits up to 250V” describes four sizes of plug rated at 2, 5, 15 or 30 amperes. The plugs have three round pins arranged in a triangle, with an earthing pin. These plugs are polarized and unfused. Plugs are non-interchangeable between current ratings, preventing a 30 ampere appliance from overloading a circuit with only a 2 amp socket. Introduced in 1934, the BS 546 type has mostly been displaced in the UK by plugs and sockets to the BS 1363 standard. The 5 A plug, and 2 A versions, are sometimes used for centrally switched domestic lighting circuits, to distinguish them from normal power circuits. BS 546 was almost universally used in the UK and Ireland for indoor dimmable theatre and architectural lighting installations, but there is now a widespread move to using IEC 60309-2 16 A industrial sockets in new installations. It was also often used where an unfused plug was desired.

 5 ampere (Type D)

5 Amp switched socket-outlet to BS 546

India, Nepal and Pakistan have standardised on a plug which was originally defined in British standard BS 546. It has three large round pins in a triangular pattern. The relevant Indian standard is IS 1293:2005 Plugs and Socket-Outlets of Rated Voltage up to and including 250 Volts and Rated Current up to and including 16 Amperes and the rated current for this size is 6 A. The BS 546 standard is also used in parts of the Middle East (Kuwait, Qatar) and parts of Asia and South East Asia that were electrified by the British. This type was also previously used in South Africa, but has been phased out in favour of the 15 A version there. In Sri Lanka, Ghana, Kenya and Nigeria, the plug has been mostly replaced by the British BS 1363.

15 ampere (Type M)

15 Amp switched socket-outlet to BS 546

The 15 A version of the BS 546 plug has larger line and neutral pins of 7.05 mm (0.278 in) diameter and 21.1 mm (0.831 in) length. Line and neutral are spaced 1 in (25.4 mm) apart, and earth is 1+18 in (28.58 mm) away from each of them. In India, Pakistan, Sri Lanka, Nepal and Namibia, the 15 A version is used for larger appliances. The relevant Indian standard is also IS 1293:2005 Plugs and Socket-Outlets of Rated Voltage up to and including 250 Volts and Rated Current up to and including 16 Amperes and the rated current for this size is 16 A. Some countries such as South Africa use it as the main domestic plug and socket, where sockets always have an on–off switch built into them. South African standard SANS 164-1 Plug and socket-outlet systems for household and similar purposes for use in South Africa – Part 1: Conventional system, 16 A 250 V a.c. defines a modernized 16 A plug derived from BS 546, SANS 164-4, defines keyed variants for special purposes such as telecommunications power. The BS 546 plug and socket is still commonly found in Botswana, alongside BS 1363.This plug is also widely used in Israel, Singapore, Sri Lanka and Malaysia for air conditioners and clothes dryers.

A socket has been developed for the Indian subcontinent that accepts both 6 A and 16 A plugs, with adjacent holes of the appropriate gauge. Sockets without a switch are uncommon in India.

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