What is Dual SIM

What is a Dual SIM & How Does it Works?


While roaming around a market or watching TV, you must have seen ads for smartphones with two or more SIM cards. This technology burst onto the scene a few years back. So, you must be aware of what is a Dual SIM phone and the benefits that come with it.

However, like many others, you may still have other questions in mind, like what its standby time is, what is Dual SIM dual active, what’s the difference between them, and how they work.

If you want to know what this not-too-new technology is, how it powers our smartphones, and its pros and cons, we’ve got you covered. This blog post is full of information, and we’ll try to answer as many questions as possible.

Let’s begin!

What is a Dual SIM?

Every smartphone should have a SIM (subscriber identity module) to connect to a mobile network. Any phone with two slots for different SIM cards working simultaneously is a dual SIM phone.

Having two SIMs in a phone means using either a SIM card to make or receive calls. Simply saying, this is a feature in some phones that allows them to use two SIM cards simultaneously.


Having a dual SIM phone is advantageous in many ways. For instance, many business people use one number for work-related calls and the other for personal calls to friends and family.

Some time back, people used to carry two phones for two different numbers: one for personal needs and the other for business. However, using a handset with two SIM cards installed is easy to carry around and manage.

Another thing why people opt for dual SIM smartphones is because they need to make abundant calls from one and use the other to connect to the internet. Some service providers offer great voice or call plans; however, their data is quite expensive, or vice versa.

Moreover, you can also combine and leverage the benefits of both. Make calls using one network and use the internet bundle of another to lower your phone bills.

If you want more mobile coverage and to stay connected wherever you are, a phone with two SIM cards is your best bet. Also, if your job or business requires you to travel frequently, you can use one card in your home country and another for SIMs that you buy in different travel countries. This is a perfect solution to get a better and more affordable service abroad.

Here’s a list of the advantages you can avail with two SIM card installed:

  1. Widened Network
  2. Ease of Carrying
  3. Multiple Service-providers
  4. Free of Blockage
  5. Distinguished Professional-n-Personal Call
  6. Distinguished Work-n-Play Bill
  7. Distinguished Text-n-Data Deal
  8. Overcoming Constraints of Missing Network
  9. Simultaneous Calling
  10. Customizable Storage

How does Dual SIM work and what are its types

Before buying a dual SIM phone, it’s pertinent to know that there are multiple dual SIM implementations in practice. All of these work differently. Some implementations trump others owing to the benefits and the technology incorporated. Let’s go through them one by one.

Dual SIM Single Standby (Passive)

The least famous implementation of dual SIM technology, Dual SIM standby, is quite old, and only low-range phones integrate it. This technology can use two Sim cards in a device; however, only one is active at a time.

Simply put, when one of the two SIM cards works, the other one cannot be reached. Manual activation is required when you want to use the second SIM. When you do that, the first SIM deactivates automatically. Passive standby isn’t used in smartphones and was used previously only in cheap phones.

Dual SIM Dual Active

It lets you make calls from both SIMs on your phone. You can also receive calls at any SIM card at the same time. Smartphones with this implementation have both SIMs active all the time, i.e. if you are making or receiving calls on either of the two, the other can still receive calls, texts, and data will also work fine.

Basically, you’ll get a notification if there’s an ongoing call on one SIM and someone calls you on the second SIM. One drawback of devices with this technology is that they come with two radio transceivers, one for each SIM.

Due to this, they eat up more battery compared to phones with one SIM slot. Moreover, as the manufacturing cost is more, the phones with this technology are pricey. For this exact reason, phones with Dual SIM Dual Active technology are hard to find.

Dual SIM Dual Standby

This technology is a mixture of both Dual SIM standby and Dual SIM Dual Active. The former allows both SIM cards to be active while using one radio transceiver. Both SIMs are active as you don’t use them, so the technology is named Dual SIM standby.

When they are in standby mode, you can receive or make calls on any of them once a SIM is busy during the call; the second experiences inactivity until the first one is not in use. This happens when both mobile networks use 2G for making or receiving calls.

However, when the mobile network(s) are 3G or 4G and don’t use 2G for phone calls, this limitation doesn’t have any effect. Although this is not an ideal scenario, it is less costly and thus widely used in smartphones.

A dual standby phone only needs an additional slot for an extra SIM card. This results in a marginal cost increase compared to a single SIM. The comparison table below will make it easy for you to understand the differences between multiple Dual SIM implementations.

Standby Active
Dual SIM Single Standby Active Inactive Active Inactive
Dual SIM Dual Active Active Active Active Active
Dual SIM Dual Standby Active Active Active Inactive


Can you use your 3G/4G data plan on both SIM cards

You can use a 3G/4G data plan on both SIM cards. However, it is based on the Dual SIM technology used in the phone by the manufacturer. The foremost thing manufacturers have in mind is the cost to build a handset model and the percentage of their margin.

Manufacturing a handset with a Dual SIM feature that supports one 4G connection and the other 2G is relatively inexpensive. 4G and 2G can easily be combined using the same frequencies in Dual SIM Standby technology.

On the other hand, if a manufacturer wants to build a smartphone with one SIM slot supporting 4G and 3G or 4G on the other, they will have to raise the processor’s capacity to support both high-speed connections simultaneously. The costs incurred for such smartphones will also be high.

Most smartphones in the market also support 5G apart from 4G and 2G connections. Those with SIM slots offering 4G in one and 4G or 3G in another require powerful processors.


With so many benefits of Dual SIM smartphones, there are also some disadvantages, which means there’s still room for improvement.

Let’s take you through some of the disadvantages of Dual SIM smartphones:

Battery Drain

One of the most significant drawbacks of dual SIM phones is that they can consume more battery power. This is because both SIM cards are always active, so the phone constantly searches for network signals from two carriers.

This can lead to faster battery drain and reduced battery life. Some dual SIM phones have a larger battery to compensate for this issue, but not all of them do.

Storage Space

Another potential drawback of dual SIM phones is that they often have limited storage space. This is because the manufacturers have to make room for the second SIM card slot, which means that the phone may have a smaller battery, less internal storage, and fewer hardware components.

This can be an issue for users who need a lot of storage space for their photos, videos, and apps.

Low-cost tech implementation

Phone manufacturing companies mostly opt for the 4G and 2D Dual SIM Dual Standy technology. This means you can use one SIM for only calls and messages, not for data connection. It also lowers the effectiveness of Dual SIM smartphones.

Compatibility Issues

Some phones may have compatibility issues with certain network operators, especially if the phone is not designed explicitly for that network. This can result in poor network coverage, slow data speeds, and dropped calls.

Before buying, check the compatibility of your phone with your preferred network operator.

Confusing Interface

Managing two SIM cards on a single device can be confusing for some users. This is because the user interface may not be as straightforward as a single SIM phone, and it can be challenging to make calls, send messages, and choose which SIM card to use for data connectivity.

Ultimately, it can result in confusion and frustration for some users, especially those who are not tech-savvy and old-aged.


Another potential drawback of dual SIM phones is that they are often more expensive than single SIM phones. This is because they are more complex and require more components, which can result in a higher price point.

Network Issues

If one of the SIM cards is not working or has network issues, it can also impact the functionality of the other SIM card. This can result in poor network coverage, slow data speeds, and dropped calls.

Additionally, suppose one SIM card is having issues. In that case, it can be challenging to determine which SIM card is causing the problem, resulting in frustration and confusion for the user.

Smartphones with this technology have several drawbacks. However, for users who need to use two SIM cards on a single device, the benefits of a dual SIM phone may outweigh these drawbacks.

Based on the costs and the features you get in Dual SIM smartphones, most models in the market are Dual SIM Dual Standby. If you are interested in a Dual SIM phone, here are some prime examples you can easily buy.

  1. Samsung Galaxy S22 Ultra
  2. Google Pixel 7 Pro
  3. Vivo X80 Pro
  4. Google Pixel 6a
  5. Motorola Edge 30 Ultra
  6. Oppo Find X5 Pro
  7. Asus Zenfone 9
  8. OnePlus Nord 2T
  9. Samsung Galaxy S22
  10. Poco X4 Pro 5G

What about iPhones

A few years back, Apple Inc. didn’t like the idea of Dual SIM on iPhones. However, all phones in their latest series, iPhone 14, support this functionality. iPhone XS, iPhone XS Max, and iPhone XR were the first models that offered this feature, following the lead of Android handsets.

The tech giant has incorporated Dual SIM Dual Standby technology in their smartphone. Meaning both SIMs can make and receive calls. Using this technology, you can use two numbers simultaneously, but this feature works in selected countries where network providers support eSIMs.

Currently, most carriers around the world offer support for eSIMs. You can see the list of these countries on Apple’s official website.

Final words

Such smartphones have become a norm. Seeing the popularity of these phones, all manufacturers have seized this opportunity and are now building dynamic handset models that support this functionality.

Now that you’ve read this post, all dual SIM implementations aren’t the same, and some are more outdated than others. So, if you plan to buy a new phone with two SIMfunctionality, do thorough research before heading toward the market.

Do let us know which phone you are planning to buy next.

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