Plug Adaptors: Uses and Limitations

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Plug Adaptors: Uses and Limitations

Where would the world be without plugs? They are ubiquitous, almost a symbol of modernity. So mundane and familiar, they only get noticed when some kind of problem occurs. Since the most dramatic kind of problem that can occur is an electrical fire, buyers should pay attention to safety issues especially in relation to mains power. Mostly though, adapters are used for convenience, and the range of applications is wide.

Keeping the focus on domestic and consumer plugs and their adaptors, there are three main arenas where plugs and adaptors can be deployed. First of all, there is mains power, the electricity that runs a modern home, office, or factory. Secondly, there are plugs that connect an array of consumer devices, such as home audio, computers and telephones. Thirdly, there are plugs that are specially designed for use in cars. All of these types of plugs need an adaptor at some time or another. Buyers in search of plug adapters should be knowledgeable about the various types available in order to buy the necessary one to meet their needs and ensure maximum convenience and satisfaction.

Mains Power Plugs and Adaptors

Perhaps the first kind of plug that comes to mind when the word is used, and most familiar type of adaptor, is the one that you need to connect to the domestic mains electricity. Because most rooms are furnished with only a limited number of power outlets, adaptors are frequently used to make it possible to use several domestic electrical devices simultaneously.

Mains Adaptors

Power sockets are a common cause of domestic fires, so not only should plugs be selected that are appropriate to the devices being connected, but care must be taken to ensure that any adaptor plugged in to a mains socket is capable of managing the load being asked of it. The usual advice regarding adaptors is to ensure that the individual plugs connected to it are between them rated at no more power than the socket is capable of supplying. Apart from cooker circuits, domestic wiring in the U.K. is geared to 13-amp sockets. Devices, therefore, should add up to no more than 13 A. The following table shows some typical domestic appliances and their normal amp rating. Note that these figures are for the plugs. The appliance may, and probably will, draw less power but never more unless it is faulty.


Fuse Rating

Clock radio, DVD player, Electric blanket, Fan, Food mixer, Fridge, Lamp, Laptop PC, PC, Radio, Table lamp, TV, Vacuum cleaner, Video player

3 amp

Coffee maker, Hi-fi, Microwave oven, Toaster, Washing machine

5 amp

Dishwasher, Hairdryer, Iron, Kettle

13 amp

It is worth bearing in mind that British domestic sockets conform to a standard that is, with a few exceptions, unique to this country. Although the loading issue is common to all domestic power supplies, the configuration discussed here is not necessarily applicable in other countries.

Adapters and Extensions

Another concern about a domestic adaptor is the number of outlets that it can support. It is interesting to note that despite the name, an adaptor that plugs directly into a wall socket does not "adapt" in the sense that some other types of adaptor do. When the adapting is displaced by a length of cable, the term used is an extension. Since adaptors and extensions are functionally equivalent, the same pros and cons apply to both.




Single way


Can only be used for one purpose at a time



Potential safety hazard if overloaded

The chart above summarises the trade-off between single-way and multi-way adaptors and extensions. Usually, adaptors have either two or three sockets available, although four can be fitted into the cubic shape they normally come in. The adaptor should have its own fuse, most likely rated at 13 A. Extensions can be bought with five, six, or even seven outlets. The larger types are intended for use with computers and their peripherals, which do not normally draw an overwhelming amount of power and as far as the peripherals are concerned, spend most of their time on standby.

Some adaptors and extensions include conditioning circuits. These are designed to reduce or eliminate power spikes and surges that can damage sensitive equipment. They are generally more expensive but not prohibitively so. Some extensions extend this protection to network, phone, and aerial cables. At the other end of the scale, perhaps the simplest type of plug adaptor is the kind that allows bathroom devices like electric razors and toothbrushes or their chargers to connect to the mains. Similar to these are surge protecting adaptors with a single aperture for a standard mains plug.

Travelling Adaptors

A different type of power adaptor altogether is the type designed for regular travellers. These devices are adaptors in the true sense, making it possible to operate UK equipment from sockets that conform to other standards. They are usually called travel adaptors, and the main destinations catered for are Europe, the USA, and Australia. There are also universal adaptors, which can be used in several, if not all, potential destinations. There are also adaptors available for traffic coming the other way, adapting to the UK standard.

There is one last type to mention, a type that might be termed time travelling adaptors. Prior to 1945, the British domestic wiring standard was for 15 A round pinned sockets. Although very few properties with round pin wiring remain, there are still a few vintage appliances with round pin plugs that people sometimes like to plug in. Note that European round pin sockets use thinner pins that are also more widely set from each other.

Consumer Appliance Plugs and Adaptors

Turning now to consumer appliances, there are three main areas where plugs and adaptors come into play: home audio and video, computing, and telephony. There is a certain amount of crossover between the latter two, especially as mobile phones share a certain amount of technology with computers.

Home Entertainment Plugs and Adaptors

The various types of lead that might be required to connect the elements of a home entertainment system are usually supplied with the correct terminator for the application they are intended for. Sometimes, though, it is useful to have adaptors available. The most common kind is to convert headphone mini jacks to full quarter inch stereo jack sockets. Often, headphones are supplied with mini jack plugs for use with portable players and an adaptor to allow them to be plugged into domestic audio equipment, which is normally equipped with the full sized jack socket.

Another type of adaptor that might be encountered, especially by musicians, is a type that converts RCA plugs to mono jacks, which then plug into the left and right channel inputs of devices, such as digital mixers. Mini jack to RCA converters can also be found. Lastly, there is one drawback that all of these audio adaptors share. They multiply the number of connections in a circuit, which in turn multiplies the number of potential contact failures.

Computing Plugs and Adaptors

With computers, the main focus of adaptor design is with the USB socket. A lot of desktop computers have PS/2 sockets for connecting keyboards and mice, usually colour coded mauve and green respectively. Often, new or replacement parts are supplied with a USB lead and an adaptor so that the user has the option of plugging into these dedicated sockets, leaving the USB sockets free for other devices. Note that the arrangement is not reciprocal. You cannot plug devices other than a mouse into a PS/2 mouse port and the same with the keyboard port. Moreover, older computers and peripherals used to have RS232 ports, the predecessor of the USB, which came in two sizes, nine pin and 25. Adaptors can still be bought to convert between the two and also between RS232 and USB.

Another frequently encountered type of plug and adaptor is used with video, although with HDMI becoming more common among graphics processing units and displays, the need for these is diminishing. Finally, one intriguing and relatively obscure plug-and-adaptor configuration available for domestic purposes is the HomePlug system, which enables users to create an Ethernet network using ordinary domestic wiring. The basic type runs at 200 megabytes per second, which is enough for a single user to browse and stream. For more interactive uses, such as gaming, there are 500 Mb/s models, and 1 Gb/s models are coming in. The limitations of the system include being less well suited to aged wiring, they do not work well in multiway sockets, and some electrical devices can cause interference.

Telephony Plugs and Adaptors

The most commonly seen telephone adaptor around the home is the one that is normally installed with an ADSL broadband package. This is supplied by the telecom company, which is responsible for its maintenance. Before ADSL, modems plugged in to the same type of socket as the landline phone, and adapters were common in order to allow both to be permanently connected although one could not use the two simultaneously.

Nowadays, with the prevalence of mobile phones, the more common type of plug and adaptor is for peripherals that might need a USB to mini-USB adaptor. Another common adaptor is for connecting proprietary headphone outputs to standard mini jack sockets and from there to the user's preferred headphones. Finally, a type that is likely to become more common as the smartphone market matures is for adaptors that can connect a smartphone to an HDMI television screen.

In Car Plugs and Adaptors

For a long time, there have been compact versions of domestic appliances that are designed to plug in to a car's cigarette lighter socket. There was little call, though, for adapters as such before USB became so widespread. Now, USB adaptors designed to fit the lighter socket are commonplace. So common, in fact, that one type of adapter that is now available splits the single power output and divides it between two sockets, each of which can then have its own USB adaptor or indeed any other device that can be powered by this type of source.

Buying Plug Adaptors on eBay

With such a variety of possible applications for plug adaptors, there is a corresponding range of searching strategies that might be employed while looking for the right product on eBay. However, starting from the home page with a search on the appropriate term may be the best way of getting started, especially for new users.

For mains electric adaptors, the kind that simply multiplies the number of outputs, "mains adaptor" should be sufficient although some exotic results may be mixed in, such as listings for disguised surveillance equipment. The filters that accompany the search results should enable you to tune those out for a better listing of results. For extensions with conditioning circuitry, there are a number of interchangeable key words that might produce similar results, such as "extension surge". Lastly, for collectors of vintage mains adaptors or people who happen to live in buildings with ancient wiring, a handy shortcut is to look for "Bakelite adaptor".


With mains adaptors the main issue to look out for concerns loading. For safety reasons, it is highly recommended that the total amperage of all the devices connected to the adaptor or extension should not exceed the maximum load that the host socket can bear. As a rule of thumb, the rating of the individual plug fuses can be totted up, but with large multiway adaptors and extensions, it might be advisable to do some research on the actual power draw of the individual appliance since it can be substantially lower than the rated plug might suggest.

When a connectivity issue arises with domestic appliances, such as entertainment, communication and computing equipment, the best thing is to figure out what the desired outcome is and to search for solutions. The chances are that someone else has had the same problem and a way of solving it is easy to find in eBay's comprehensive listings.

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