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How do dual SIM phones work?

  • 3 May 2019
  • 1 reply
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How do dual SIM phones work?
iD Mobile
iD Mobile Employee
We all know what SIM cards are – they manage your number and network connection. But what are dual SIM phones? And more importantly, how do they work? Let’s go ahead and find out.

What is a dual SIM phone?

A dual SIM phone is a phone that can handle two SIM cards at once - which is ideal for anyone who has two different numbers or data plans. Let’s say, for example, you needed one SIM card primarily for calls and texts and the other has a big data package which you use to browse and use social media with. With a dual SIM phone, you can switch between them depending on what you need at the time.

Other examples where you’d need a dual SIM phone is if you had a work number and a personal number, or if you travel frequently and need to switch to the local SIM card as soon as you arrive.
But in true dual SIM fashion, there are not one but two types of dual SIM phones. You’ve got DSDA and DSFA.

How do DSDA phones work?
DSDA stands for Dual SIM Dual Standby and means that when you’re using one SIM card, the other is on ‘standby’. That means if you get a call on SIM 1, SIM 2 will be put on standby, just like if you were engaged or on another call.

Also, only one SIM card can be connected to the internet at a time. However, some phones do offer a ‘Hot Swap’ feature, which lets you choose which SIM card to use for data in the settings. If your dual SIM phone doesn’t have the ‘Hot Swap’ feature, then you will need to make sure that one you want to use for internet is always in slot 1 – because only the primary SIM will be able to connect.

How do DSFA phones work?
DSFA stands for Dual SIM Full Active and lets you connect to both SIM cards so you could get a call on either lines at the same time. If you get an incoming call on one line during a call on the other, you’ll get a little alert and can decide which call to take. You should know – there aren’t many of these types of devices around though.

Can you use SIM cards from two different networks?
That all depends on the device you’re using. Some phones are ‘locked’ to one network, which means it won’t accept a SIM card on another provider. If that is the case, then you’ll have to use two SIM cards that are on the same network.

What features about dual SIM phones do you like the most? Let us know in the comments below.
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1 reply

  • Active Contributor
  • 35 replies
  • May 5, 2019
I always wondered what the benefit of a dual sim phone was because years ago a friend of mine had one and he had to turn his off and then back on after clicking a switch on the back to select a different sim - and I thought that seemed to be a pain. These you are describing which can switch on the fly or even show you incoming calls from the different sims at the same time sound so much better. I have always managed to get a package that suits me on both minutes and data, so don't need 2 UK sims, but I can see how it would be useful for a travelling when you might need a foreign sim as well as a UK one so I would definitely look into this in the future. Jase