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When looking at smartphone specifications, you may notice that some phones are said to be dual SIM smartphones. Not only that, the dual SIM smartphones come in varieties such as dual active and dual standby.

If you’re unfamiliar with dual SIM technology, that can be a bit confusing. However, it’s pretty simple. A dual SIM dual active smartphone can use two SIM cards and keep them both active at the same time, even when in use. A dual SIM dual standby smartphone can only keep two SIM cards active at the same time only if they’re both on standby.

Compared to a decade ago, there are quite a number of dual SIM smartphones today. If you’re looking to buy a dual SIM smartphone, it helps to know what kind of dual SIM smartphone to get, and what you can do with it.

What is a dual SIM smartphone?

dual sim phone

A dual SIM smartphone is a mobile phone that has space for two separate SIM cards. Depending on the phone, the two SIM cards can be active at the same time and even make and receive calls at the same time.

The terms ‘dual active’ and ‘dual standby’ are used to describe the phone’s ability to perform functions on both SIM cards at the same time.

Types of dual SIM technology

There are three types of dual SIM smartphones:

Dual SIM standby (DSS)

A dual SIM standby smartphone is capable of using two SIM cards, but only one card can be used at any given time. The user is required to specify which of the two SIM cards is able to make and receive calls.

That means that when one SIM card is working, the other is unreachable. You can’t make or receive calls from it. You can’t send or receive SMS texts. You can’t use mobile data on that SIM. To use the second SIM card, you need to activate it manually and deactivate the first SIM card.

DSS is a rather poor implementation of the dual SIM technology that, fortunately, is not commonly found in today’s smartphones. It’s an old technology that was used in older mobile phones.



  • At its core, dual SIM standby technology simply allows you to have access to two SIM cards inside one phone, which is more cost-effective than carrying around two smartphones. 


  • You cannot use two numbers at the same time. When one SIM card is active, the other cannot be reached. This beats the purpose of having two numbers because you ideally want to be available on both of them at the same time.

Dual SIM dual standby (DSDS)

A dual SIM dual standby smartphone takes the DSS technology to the next level. DSDS allows your smartphone to have two active SIM cards that can both be reached at any time, as long as they’re both in standby mode.

Dual SIM dual standby smartphones use only one radio transceiver for both SIM cards. For this reason, when one SIM card is on a call, the other will be unavailable. It will become available again once the active SIM card is off the call and back on standby. As long as both SIM cards are in standby mode (i.e., not in use), you can make and receive calls on any of them.

This limitation, however, is only limited to mobile networks that use 2G technology for voice calls because 2G voice calls use circuit-switched data connections. That means that when a SIM card is active on a call, it will use the transceiver exclusively.

3G and 4G mobile data connections, on the other hand, use packet switching data connections. That means that when using 3G or 4G mobile data on one SIM card on a dual standby smartphone, the other SIM card will not be disabled.

The dual SIM dual standby technology is the most commonly found dual SIM system in most of today’s smartphones.


  • Dual standby technology allows you to use two SIM cards simultaneously. You can receive calls on any number at any time, as long as both SIM cards are on standby.
  • Because both SIM cards share the same transceiver system, it saves on space inside the phone. That can also drive the price of the smartphone down because there is no cost of manufacturing a whole other transceiver system involved.
  • Another thing you save on is battery life. Because there’s only one transceiver to provide power to, there is no additional strain on the smartphone’s battery, thus giving you more juice to keep your phone running for longer.
  • If you’re using a 3G, 4G, or 5G mobile network to make voLTE voice calls, you can receive calls on both SIM cards at the same time, even if you’re already on a call on the other SIM card.


  • Although you can receive voLTE calls on both SIM cards at the same time, you can’t put them on hold or add them to a conference call.
  • And if you’re using a 2G network to make voice calls, you cannot receive a call on one SIM card while still on a call on the other. They both have to be not in use for you to receive a call on either SIM card.

Dual SIM dual active (DSDA)

This version of the dual SIM technology enables you to make and receive phone calls from both SIM cards. DSDA smartphones have both their SIM cards permanently active and ready for calls or data.

That is made possible by the fact that dual SIM dual active smartphones have two transceivers, one for each SIM card. So, when one SIM card is engaged on a call, the other remains active using its own transceiver.

That means that if someone calls you on the number of SIM 1, you can still receive another call on SIM 2’s number on the same phone. You will get a notification of the incoming call. From there, you can choose whether you want to answer the call, put it on hold, or add it to the existing call to initiate a conference call.

But as much as DSDA sounds ideal, it’s not that common in the market. It is very difficult to find a dual active smartphone, especially high-end ones.


  • The biggest advantage of a dual active system is that both SIM cards can be reached at any time, even when you’re already on a call on the other SIM card.
  • You can manage calls from both SIM cards at the same time or even add them both to a conference call.
  • It also doesn’t matter if you’re using 2G or 4G, both SIM cards will always be active. That’s because each SIM card has its own transceiver which it can use exclusively.


  • Because a dual SIM dual active smartphone has a transceiver for each SIM card that’s always active, there is an increased demand on the phone’s power resource to keep the system running.
  • The cost associated with implementing a dual active system is considerably higher than with any of the other two types. That means the cost of the smartphone will be considerably higher

Which is better?

Each system has its advantages and disadvantages. However, most smartphone OEMs (original equipment manufacturers) have opted to go for the DSDS system, and for good reason.

If you look at the smartphone market as a whole, the portion that makes up people who need two SIM cards to be active constantly to make conference calls between the two is very small. It doesn’t make sense to drive up the costs of production just to satisfy such a tiny market.

For most people who benefit from dual SIM smartphones, the dual standby technology is sufficient enough to satisfy the basic needs of using two SIM cards at the same time on one device.

Can a DSDS smartphone work like a DSDA smartphone?

Yes, a dual standby smartphone can work just like a dual active smartphone, but only to a certain extent in the right conditions.

Some mobile companies use voLTE (voice over LTE) for making voice calls. This technology uses the 4G network for voice calls. And as previously mentioned, 4G does not require the exclusive use of the transceiver.

So, if you’re connected on a call using voLTE on one SIM card, it is possible to receive another call on the second SIM card. You will get an incoming call notification, just like you would with a dual active smartphone.

The only difference is that when you’re on a call on a dual standby phone using voLTE, you cannot hold a conference call that combines calls on the two SIM cards. Only a dual active smartphone can do that.

Is a hybrid dual SIM smartphone dual active or dual standby?

hybrid dual sim

A hybrid dual SIM smartphone is, in essence, very similar to a dual SIM smartphone in that they both have room for two SIM cards. The only difference is that the second slot of the hybrid dual SIM system can either take a SIM card or a microSD card.

Other than that, the two technologies work pretty much the same. Therefore, there is no reason why a hybrid dual SIM smartphone can’t be dual active or dual standby. That’s entirely at the phone manufacturer’s discretion.

That being said, dual active smartphones in general are rare. Chances are you will struggle even more to find many hybrid dual SIM dual active smartphones on the market.

Are dual SIM smartphones even necessary?

Dual SIM smartphones may not be for everyone, but for some people having one can be useful. For instance, a businessperson who has a work number and a social number can have them both active at the same time on one smartphone instead of carrying around two devices.

In some regions, certain mobile companies may have better voice plans than others, while other mobile companies may have better data deals. Having a dual SIM phone in such a market allows you to take advantage of both deals and possibly save on how much you spend on your phone.

Another advantage of using two mobile providers at the same time is when travelling to a foreign country because it allows you to keep your home country SIM in your phone and also insert your destination country SIM in your phone.


Dual SIM technology can be very useful indeed for those who really need it. And if you’re in the market for a dual SIM smartphone, chances are you might end up with a dual standby model because of their popularity and not a dual SIM dual active smartphone. But that’s okay. For the most part, a DSDS technology works just as well as DSDA.

But to the average person who only ever uses one number, it really doesn’t make a difference. Any type of phone SIM technology works just fine.

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