Below is a brief overview of dual SIM mobile device and how they work:

What does a UK dual SIM phone mean? 

A UK dual SIM mobile phone is just as it says: one single mobile device that provides the option to change between two different UK SIM cards.

In the UK most mobile phones that are sold in the high street stores sold have just a single SIM slot.

To someone who lives elsewhere in the world you are maybe wondering how anyone survives with only one SIM card. And so here are some reasons why you should have a UK dual SIM phone:

Some people just want two mobile phone numbers! Why would someone want more than none number? Why is one number not enough?

There are some logical reasons for having two numbers…

There can be problems moving from or switching your network provider and the requirements change from country to country with regards to mobile network compatibility. This is the main reason why dual SIM slot phones appear in some parts of the world and not others. 

In recent years some countries have made it difficult to change jump from one mobile network to another.  A way around this was to contract with a new provider and use the second SIM slot. Here in the  UK we have luckily been able to enjoy the freedom to move between different mobile networks and with the added bonus of being able to take our current number with us.  All this is thanks in  part to the UK law since 2003. The same kind of legislation has just recently been received in some countries and in some cases not at all. And so when mobile phone owners in these parts have switched network provider they must purchase a new SIM and contract a new provider. They need to keep their existing SIM card running to ensure that they are still contactable by everyone who has the original number.

Concerns over coverage

A common issue and reason for requiring UK dual SIM phones is the quality of the coverage the service provides. Because of the sheer physical size of countries there is no one mobile network which has entire coverage. Even in the UK which is heavily covered rural areas still have issues.

When a person has two UK SIMs it gives the advantage of two mobile network providers that may be available in different areas of the country. 

Separating work from private life

Another very valid reason for needing a dual SIM phone is for keeping your work and personal life totally separate. Very common amongst those of us who run a business from our mobile phone.

Two SIM cards enables you to manage calls and messages for two numbers separately meaning that you also have the choice of who to give which number to. 

Not mixing business with pleasure

UK dual SIM mobile phones are also an easy way to carry just one phone and all while keeping your work and private life separate. In this case it gives you the power to not give out your personal to just anybody and keep tele marketers at bay. 

A dual-SIM phone allows you to use both a temporary UK SIM for data and local calls while keeping your personal SIM from home in your phone for friends and family or any other personal reasons such as dating, house hunting, social, etc. This means that anyone at home can reach you immediately and cheaply and you can chat with local friends without the dreaded roaming costs. This solution is totally practical and budget friendly and with the added bonus of not having to carry two separate devices.  

A dual SIM phone makes going on holiday or overseas simple. All you have to do is keep your regular SIM card in your phone and then simply buy a SIM card local to the country you are in  and insert it in the second slot.  This makes it cheap to stay in contact with travel companions and be in contactable for local contacts. Plus, you will still be accessible to your friends and family back home as they can still call or text without footing a bill for international calls. 

Of course, there are many other advantages for using UK dual SIM phones and these are simply a few examples. Dual SIM phones are a fool proof way to ensure you are always available and contactable. So, are all UK dual SIM phones the same? No and there are two main differing types:

First type is referred to a passive dual SIM and this is when a phone has an individual and shared antenna for both of the SIM cards. The two SIM cards spend the majority of their time in a passive mode (or standby) until they need to be used.

When one of the SIM cards gets used for either data or voice purposes the other SIM card instantly inactive. This means you can´t download data while making phone calls simultaneously.  Might sound like it is a hassle but in reality, it really doesn´t cause any major inconvenience. If one of the lines is busy and therefore unavailable to take a call then it is more than likely going to be automatically diverted to voicemail by the mobile network provider.

This popular and cost-effective type of UK dual SIM phone can be purchased from a range of popular manufacturers such as Motorola, Huawei, Nokia and Microsoft.

Second type od dual SIM is referred to as active and this type refers to mobiles which gain from having an antenna for each SIM slot ie. two in total. This allows the mobile phone user to use the two SIM cards at exactly the same time. This is for instances such as making a phone call on SIM number one and downloading something with SIM card number two. It is even possible to have two conversations at once and switching the calls and putting one of the calls on hold if need be. Disadvantages with this type of UK dual SIM phone include the main one being running cost. An extra cost is incurred with having two antennae built into a mobile phone. A user will also have issues with frequent low battery due to the cellular connections basically doubling.  problems as the 

Then there is the problem with availability of such type phones. In some countries such as the UK they are almost impossible to find. Take for example when HTC released a Desire 600 with Dual Active SIM card slots and this was never available to purchase in the UK. Quite simply if you absolutely need an active dual SIM phone you will have to be prepared to give up might sacrifice high end features and end up buying from a not so popular or mainstream brand. 

You should also consider that before buying a Dual SIM phone to check if both slots can use 3G/4G connections.

You will also find that quite a few manufacturers combine the SD card and second SIM card slot to make a hybrid slot. Generally speaking, this is done to preserve space as the slimmer the phone the better. It helps improve looks but costs functionality as with this you will have to choose either a second SIM card or an SD card in order to extend storage space. 

In brief there are some disadvantages with using dual SIM phones but for most people who really require this type of mobile phone the benefits outweigh them such as being able to manage your calls and get the coverage you need in areas with low quality reception. More and more of the bigger brands are now offering this dual SIM type of phone. When a second SIM card is installed, the phone either allows users to switch between two separate mobile network services manually, has hardware support for keeping both connections in a passive or standby phase state for automatic switching or has individual transceivers for keeping the two individual network connections at once.

In many countries outside of the UK, dual SIM phones are pretty much mainstream as where phones are normally sold as unlocked or not locked into any one provider.  Dual SIM phones are perfect for separating work and private communications in places where there are lower call costs between customers of the same mobile network and where a single network may be lacking in extensive coverage and also for travel across national and regional borders. 

You will want a UK dual SIM phone if you no longer want the hassle of carrying to carry two separate handsets and usually two separate chargers with you. Or maybe you don´t like having to remove the back cover and battery just to change the SIM card.

Also, if you really love the idea of just one mobile but two different numbers and profiles ie. One for business and one for personal life. 

The two SIM cards can be connected to different networks or of course – they can be the same network but no matter what, it is ultimately your phone and your choice and your preferences. For example; a viable option would be a Pay As You Go (PAYG) plan on one of the SIM cards and a long term monthly on the other SIM card. This is common for mobile phone users who need to share their mobile device handset with a team member or a family member. Also, a popular choice for having a contract for your business calls and a PAYG for private calls. 

Or another scenario would be that Instead of using one SIM card for work and one for private use, you could use one SIM card for placing voice calls and the other SIM card for text messaging.

But why would anyone want to do that? Well, because maybe one network has a low voice calling costs and the other network provider might have a cheaper deal on text messaging plans.

The future of dual SIM card phones?  Bearing in mind that the first mobile phones were buy, big and heavy but despite this they were indeed an extremely useful technological leap at the time. Nowadays mobile devices are becoming smaller, smoother, lighter, finer and totally reliable with an ever-growing list of functions and features. And Tri-SIM (triple-SIM) devices are already in the development stage and will be launched on to the market where your mobile device can have three SIM cards. 

Also beneficial is the fact that with having a dual SIM phone, users can keep two separate lists of contacts on each SIM. Roaming is also easier by being able to access a foreign network while still keeping the original local card. Sellers of foreign SIMs for travel purposes usually encourage dual-SIM operation with a home country and a local SIM both in the same device and at the same time. When you have a dual SIM it makes going abroad easier as it just means connecting to the travel SIM card which you put in the second SIM slot of your phone. You choose when to switch it on for all services or simply just choose to switch on your preferred services that you use and need the most such calls or data. There are limitless reasons why you may want or need more than one SIM card in one single device but the most common reason is pretty simple and obvious and that is  for just having two numbers because you might want to have your work phone number and your private number on only one phone and not have to always have two separate handsets and the respective chargers. Contract and maintenance costs significantly drops too. Dual SIM phones are most used in India and Indonesia. According to online sources the breakdown is as follows: Egypt (51.72%) India (66.61%), Ukraine (55.22%) and Indonesia (65.81%), are the top countries where dual SIM phones are more popular than single SIM phones. countries where dual SIM smartphones are popular include Malaysia (48.02%), Brazil (35.8%), Philippines (35.39%), Nigeria (47.95%), Nigeria (46.38%), Poland (26.03%) and Russia (34.46%). In countries where dual SIM phones are not so popular, it is these countries that iOS devices are more popular than Android ones. Some parts of the world such as UK, Canada Japan, Ireland and the States just appear to not have any particular need for a second SIM in their mobile phone.