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Dual SIM mobile title

Dual-SIM is the term for a device that can operate 2 separate SIM cards concurrently, giving the user an option to use one of the two different lines. This can be particularly useful for users wanting to use two distinct phone numbers whilst only working from one device, or for users with internet data separate to their mobile carrier.

Although not all Dual-SIM devices work in the same way, the premise is the same; two SIM card ‘slots’ inside one device.

Dual-SIM devices are by no means a new technology, however the technology has seen a revival over the last five years with the introduction of more SIM free mobiles, tablets and smartphones hitting the market. The technology has been particularly popular with phones from the Far East which are based on open source operating systems like Android or Linux.

Why use Dual-SIM?what is dual sim image

So why would you need to use Dual-SIM products?

Second Line– Currently the most popular use for Dual-SIM is with business mobile phones running two ‘lines’. This allows the user to have both a personal and business phone number within the same phone. Users can place a their ‘work’ SIM card in the phone alongside a personal SIM, meaning they only have to carry one handset but have the freedom of a personal and business number.

This can also be particularly useful for those users who have two jobs/roles, needing two separate phone numbers.

The best dual-SIM phones allow the user to automatically switch between the two SIMs (basic ones may need a physical switch between the two lines).

International Tariffs-Another popular use for Dual-SIM is for international network hopping. If you’re a frequent flyer and need to add a separate cheaper SIM for a particular country, or simply a more internationally friendly tariff (travel SIM), Dual SIM phones allow you to carry both lines in one single phone. This keeps your primary number contactable with the addition of a cheap(er) international tariff for use on the go.

Data Packages– If you’re a heavy data user, it’s often worth investing in a separate ‘internet data only’ SIM so you don’t accidently rack up a sky high bill on your primary phone bill.

Dual-SIM devices allow users to switch between the two SIM cards depending on the task you’re up to. Meaning you can switch from your primary phone line to a the cheap data card if you fancy a bout of streaming.


Myths and Misuse

There are a number of myths and rumour circulating around about Dual-SIM and its usage, so lets clear a few up.

Internet ‘Boost’- There is an established rumour doing the rounds that doubling up on a 3G(or4g) SIM will ‘boost’ your internet connection. This simply isn’t true as the two lines work completely separately, in fact many dual-SIM phones don’t even have an active high-speed data connection on the second SIM slot.

Double line – Not all phones are created equal, so this is where you need to check with the individual phone or tablet you’re looking to buy. Most, Dual-SIM phones have two active, or live, slots. This means both SIM cards can be used simultaneously.

However if only one slot or line is active (Live), it means you can only use one at a time. For example, to access SIM 2, you’ll need to turn off SIM 1. The process is usually very simple, but worth noting when you shop around.


For more info on smartphones and Dual SIM mobiles on offer, check out our smartphone guide at ebuyer.com.



  1. Mention of international phone use reminds me that a factor almost never mentioned is the regularory compliance of phones. Different countries have different cerification standards.
    Most or all eu countries as far as I know have a common standard but the far east for example is different.
    You need to check the marking that is usually found on a label that is under the battery where this is removable.
    If you buy a phone in Europe it is likely to be CE cerified for Europe but illegal as a phone in Japan for example.
    I think very often you will be OK with WiFi and luckily internet calls such as those over Skype are more cost effective than using the phone with your UK provider. You could In theory use a locally sourced sim in your phone but that can be hard to find and potentially illegal.

  2. I recently moved to the WileyFox storm – dual SIM Android Cyanogen … has its little quirks but is one fabulous phone … would recommend for anyone considering a dual SIM device

  3. My main requirement was to overcome poor receiption in a rural area. However dual sims are still proving useful now that the signal strength has improved.

  4. I have a Cubot X9 dual SIM phone. One slot has an Orange SIM card which I have free text on, the other is 3 network SIM for calls ( 3p/min and data 1p/MB). Both SIMs are active and you can configure which SIM is used for what activity.

    I would highly recommend this phone as it has been pretty flawless for over 12 months now and a steel at the price. Cubot’s latest phones look even better specced too.

  5. Mike,
    Yes, you can – obviously depends on phone.
    Huwaei and Honor dual sim phones have the ability to set 1 SIM for default voice calls and SIM2 for data or vice versa, or you set the same SIM to do both – the choice is yours.

    One thing to note that isn’t mentioned in the write-up is that there are Dual “active” SIM models and Dual “standby” models.

    Dual Active – means both SIMs can receive calls at same time, so if you are on a call on SIM1, SIM2 will ring as a call waiting.

    Dual Standby – Means either SIM can receive calls, but when you are talking on one SIM the second one is diverted to voicemail or can be forwarded (at extra cost) to your other mobile if someone calls SIM2.

    Also, if the dual SIM handset has 3G / 4G for data, you can only use one SIM for the data connection. You can change the default from SIM1 to SIM2 and back again, but will require disconnect and re-connect to the mobile networks.

    From personal experience:
    Honor 6 Plus = Dual Active SIM (note no 800Mhz 4G)
    Honor 5X = Dual Standby SIM
    Huawei Mate 8 = Dual Active SIM
    Motorola G4 Plus = Dual Standby SIM


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