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Old British type (BS 546*) |
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Old British type (BS 546*) |
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| Type
D refers to the 5A
version of the BS 546 plugs and sockets. There is also 2A variant. Type M refers to the larger 15A version. In South Africa this type is now rated up to16A. This page shows various 3-pin BS 546 plugs and sockets. A separate page covers non-earthed 5A BS 546 devices. |
| 1, 5 | BS 546 15A socket and plug. The socket was bought in Malaysia. Inset: compulsory label that specifies certification according to Malaysian Standard, provided by SIRIM Berhad (Standards and Industrial Research Institute of Malaysia). |
| 2, 6 | BS 546 5A socket and plug, bought in Ireland. This specimen has shutters over the live and neutral slots. They are opened by insertion of the longer earth pin. The triangular orientation of the three slots results in polarized sockets and pins, i.e. live and neutral cannot be reversed. |
| 3, 7 | BS 546 2A socket and plug. Nowadays 2A sockets are rare. It has been donated to the museum as a result of an ask for help. See acknowledgments. |
| note | Each BS 546 type of plug fits only in a socket
with a corresponding rating. Pin dimensions of the three variants are
summarized in the table below. For safety reasons the proximal half of both
the live and neutral pin is insulated. BS 546 plugs are not fused. |
| 4, 8 | A rare example of an 15A socket and plug bought in 1998 on a market in Xi-An, Peoples Republic of China. The configuration of the earth, neutral and live slots are identical to a genuine M-type socket (as no. 1), but the slot diameter is too small (earth = 7.5 mm, N and L = 5.8 mm) to accommodate a British 15A plug (see table below). Length of pins differs considerably from standard BS 546 plugs. |
| * BS 546 Until the late 1950s residences in the UK, Ireland and many parts of the Commonwealth were provided with plugs and sockets defined by the British Standard No. 546 (BS 546). Because of a change in wiring of domestic electrical systems - from radial to ring circuits - BS 546 (round pins) was replaced by BS 1363 (plugs with rectangular pins; always fused). The page on type G (BS 1363) plugs and sockets gives the details. Read more about radial and ring circuits on the ring circuits page. BS 546 is now known as the Old British, or type D (5A), or M (15A). In the first half of the previous century many countries were electrified by the British according BS 546. Some countries still use it, others have adopted BS 1363, and in some countries a mix of "old" and "new" can be found. See site http://countrycode.org/ for details. BS 546 consisted of five different versions: 2A (3 pin), 5A (2 and 3 pin), 15A (3 pin) and 30A (3 pin). Their characteristics are given at the bottom of the page. The 2 pin 2A plug has become obsolete (replaced by the 3 pin variant). The 2 pin 5A plug has become the UK shaver plug (BS 4573). The 15A variant is still applied in the UK in situations where sockets and plugs are build-in and/or a part of complex circuits (for example in theater wiring), in which it is difficult to trace a blown plug-fuse (BS 1363 plugs always have a fuse). Occasionally 2A and 5A devices are still used in the UK for centrally switched domestic lighting circuits, in order to distinguish them from normal power circuits. Originally BS 546 sockets were not shuttered, but BS 546 sockets sold in the UK and Ireland today have to be provided with shutters. Sockets may have an on-off switch. The 30A variant was used for (semi-) industrial equipment. It is now replaced by high current and multiphase sockets and plugs defined by the international IEC 60309 standard. |
| BS 546 5A, 2-pin plugs and sockets are shown on a separate page |
| Fused BS 546 plugs In contrast to BS 1363 (see above comments) by far the most BS 546 plugs do not have a fuse. However, starting in the 1950s also fused 5A and 15A BS 546 plugs are offered as an extra means of protection on circuits that were not yet rewired from radial to ring. The fused plugs shown below have been donated to the museum, see Acknowledgments. |
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| 9, 10 | 15A BS 546 plug with a 5A BS 646 cartidge fuse. A cavity, indicated by the green arrow, offers space for a spare fuse. 15A plugs have a 5A fuse, rather than 15A, because a 15A fuse would offer no more protection than the main fuse on the distribution board. The type of fuse differs from BS 1363 plugs, which BS 1362 fuses are larger. This Bakelite plug probably dates back to the 1950s. |
| 11, 12 | 5A BS 546 plug with a 5A fuse. Note that fused BS 546 plugs have a rectangular shape, in contrast to the triangular, non-fused counterparts (see nos. 5 and 6). Plug nos. 9-12 are made in England by MK Electric |
| More 3-pin BS 546 plugs, adapters and multi-plugs |
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| 13 | Plug of a power cord meant for double insulated appliances. The plug has a non-conductive 'earth' pin, which is needed to open the safety shutters and to enforce the correct orientation of live and neutral pin. The official name of a non-conductive pin is an Insulated Shutter Opening Device (ISOD). |
| 14 | BS 546 plug, rated for 16A, 250V. Note that the power pin insulation are missing. This plug was bought in Tanzania. |
| 15 | An older, Bakelite type of BS 546 15A plug. This is a so-called Clix plug. Neither a screwdriver or any other tool is necessary to attach wires to the pins of Clix plugs. See the photos and description of a 5A 2-pin Clix plug for explanation. |
| 16 | 15A, 2-way converter plug (the second, top side set of slots is not visible), which allows the use of BS 1363 devices in a house equipped with BS 546 sockets. According to BS 1363 standards converter plugs are provided with 13A fuse. |
| 17 | 5A BS 546, 3-way multi-plug. The plug has been donated to the museum, see Acknowledgments. |
| 18 | 5A BS 546, 2-way multi-plug. Additional top side slots accept flat blade type A plugs, Europlugs (loosely!) and Schuko plugs (but without earth clip connection). Both nos. 17 and 18 are made of Bakelite. The plugs are not fused. |
| 19 | Top: 5A BS 546, 2-way multi-plug. Bottom: inside of the same plug showing the copper strips and connectors. This is an example of a multi-plug in which both outlets have the same, correct orientation of live and neutral slots. Be aware that occasionally you may find more simple devices whereby the two outlets are mirror images of each other and only one of both has the correct L-N orientation. See for example image no. 7 at the page on type E plugs and sockets. |
| Ask for
help The museum is still looking for BS 546 30A devices. If anybody can help me with missing BS 546 plugs and sockets, please contact me. See about the collection for the address. |
| Characteristics of BS 546 plugs | 15 Amp 3-pin |
5 Amp 3-pin |
5 Amp 2-pin |
2 Amp 3-pin |
| Diameter of L and N pins | 6.9 mm | 5.1 mm | 5.1 mm | 3.7 mm |
| Diameter of earth pin | 8.4 mm | 7.1 mm | n.a. | 5.2 mm |
| Distance between L and N pins | 25.8 mm | 19.0 mm | 17.6 mm | 14.7 mm |
| BS 546 5A, 2-pin plugs and sockets are shown on a separate page |
| Notes 2-pin (non-earthed) 5A plugs do not fit in an earthed 5A socket, since the distance between live and neutral pins is 1.4 mm smaller than the spacing in 3-pin (earthed) plugs. Modern 3-pin BS 546 plugs always have a side entry cable, rather than a top entry. This feature makes unplugging by tugging on the cable nearly impossible. The same safety measure is found on BS 1363 (type G), and many Australian plugs (type I). |
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