How the world phones: handsets with multiple SIMs

Here's a really interesting look from Younghee Jung at the global phenomenon of multi-SIM phones that can talk on multiple networks at once. Some people get these SIMs because they want to take advantage of low-cost calling within an single network (which means that you have to keep track of which network each person in your address book uses!). Others use it to establish priority -- a business man who has a "private number" for his best customers that he always answers. Sometimes, it's just a way to get a bargain, loading up prepaid minutes on different SIMs depending on who's got the best deal. A sketch from a Liberian refugee camp in Ghana depicts an "ideal phone" that holds four SIMs.
Many mobile network operators offer cheaper rates for inter-network calls, especially in markets where competition among network operators is high. Highly cost-conscious consumers naturally get multiple numbers for cheaper calls. While it may not take too much effort to acquire the new number itself, this comes at a cost of efforts and skill: Remembering, or identifying who in your social network has the number belonging to a specific network operator. People develop a tactic, such as indicating the network operator in the name stored on the phonebook. This is not an exclusive behavior only for the developing economies, however. When the 3G network was newly introduced in Japan several years ago, many Japanese consumers also owned two numbers, one from 3G for cheaper messaging & data connection, another from existing network for cheaper voice calls.
Use of Multiple Mobile Phone Numbers (part 1) (via Kottke)


  1. dual sims is also useful for traveling especially in Europe or across the Atlantic.

    Dream phone for me would be a ruggedized Nokia N900 with dual sim HD or VGA out instead of composite and just maybe FRS radio for local chat.

    that would end up being:
    -Dual SIM
    -USB host/slave with bulk storage mode(USB on the go)
    -WiFi A,B,G,N (host, client, mesh, ad-hoc, amateur radio drivers too)
    -IRDA, not so much for data anymore but to remote control TV’s
    -FM transmit and receive
    -Quad band GSM and 3G
    -Well developed fully open community Linux/Unix distro and software
    -Great web browser
    -Video/TV out for travel desktop use via bluetooth or USB mouse and keyboard
    -Hardware keyboard
    -Rugged and water resist
    -replaceable parts like vibrator, speaker, mic, power, and USB ports(old Nokia style)
    -Separate power in port for when USB is in host mode
    -eInk secondary or primary display and ultra low power mode for book reading
    -LCD display for multimedia and dynamic applications
    -Multimedia player, ultra low power mode for audio and indexing for podcasts
    -Great camera
    -ZigBee or other ultra low power protocol for interfacing bicycle and exercise sensors
    -Digital compass, gyros, and accelerometers
    -Massive battery
    -FRS or 70cm amateur radio low power
    -Software radio driver modes for all onboard radios(wishful)
    -Power protection from overvolt and reverse polarity (DIY chargers)
    -Good car and bicycle mounting options

    I am sure I could think of more, too bad it looks like Nokia is abandoning its line of such phones for mediocre to crappy windows mobile.

  2. Sure, it’s useful, but how often you have to charge the phone! With 4 SIM-Cards, I would say every 6 hours. Or you can use a really big accu, but no one wants a big mobile phone. Good idea, but we have to wait for high perfomence accus.

  3. In Ghana, where the picture was taken, you don’t have to remember who is on which network. For cell phones the country has no area codes. Instead the first two digits of a person’s phone number indicates who their cell phone provider is. MTN(24), Tigo(27), Vodafone(20), and Zain(26) are just the most popular providers amongst many more. I know it works like this in other West African countries as well. My phone can only handle one SIM at a time but friends of mine with multi-SIM phones have figured out a way to program their phone to use the optimal SIM based on the carriers two digit code. They just dial and the phone chooses the SIM depending on the number.

  4. Hey Liberian kid, no point in launching this as a four star ‘Nokia’.

    Just go ahead and start your own company mate, don’t bother with the big ones. The big handset makers are far too cautious about upsetting their telecom buddies. Your idea could increase competition between service providers so doubt Europeans will consider it.

    1. In many countries “Nokia” is just another word for cell phone. Like Kleenex and Q-tips in the U.S. for example.

  5. When you’re extending the amount of phones to 6, and use them as ‘digital bits’ while making missed calls in parallel, a 6-bit communication protocol with 64 messages comes into existence. A concept developed in Cameroon, Afrika:

    Free, but foremostly, fully untracable mobile messaging and communication!

  6. My girlfriend, from Thailand, has a phone with two SIMs. When we first met in Thailand she gave me her number, which I used regularly, and then she started calling me using a different number, seemingly randomly.

    I inquired eventually… I thought she was using her sister’s phone at first, and didn’t realize she had two sim cards. I then got calls from her sister’s two sim cards too, so I figured there must be something else going on and had to ask :)

    As has been said, she uses it to get the best rates. She has a (inexpensive) regular monthly plan on one sim card, and the other is a pre-paid that apparently has better rates for certain things or at certain times.

    Also, the pre-paid sim cards are so cheap that they’re essentially disposable – you can give out your permanent number to your friends, and your other number to others. If you want to get rid of everyone who only knows your disposable number, just get a new sim card (which will cost you about $3 in Thailand).

  7. Dual-SIM phones were relatively common in Europe a few years ago among professionals and salespeople.

    That was before carrier subsidies became widespread, completely changing the game; phone manufacturers became the carriers’ bitches. Nokia somehow understood this perfectly and implemented huge carrier-friendly strategies everywhere (except in the US, for some weird reason). Then the iPhone happened.

    Today, I’d kill for a dual-SIM iPhone.

  8. Dual SIM adapters have existed for a few years now, they are less than $10


    but there are many others out there

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