Nov 23

EDIT: Read bottom of post!

I have been toying around with GSM modems for some time – working on the Rotary Cellphone project, i settled on the SIM900-module from SIMCOM.

Milled SIM900-board

Early in my quest, i mistakenly read, that the SIM900 was Quad band, and the SIM900A was Dual band. As I decided that i did not need the Quad-band capability, i ordered the SIM900A-modem, as it was a few $ cheaper.

Ordering the first module from far east (AliExpress) my choice was the SIM900A model. I milled a breakout-board for the GSM-module, soldered it on, and everything “seemed” to work, but i could not register the modem on the Danish GSM-network. It acted like it was locked to a specific GSM-vendor.

The modem being brand new, ruled out the option that someone else had a go at it, so what was happening ?

I trawled the documentation at SIMCOM, and couldn’t readily find any information on what the differences between a SIM900 and a SIM900A-model were.

Some helpful people at the local Hackerspace mailing-list soon found the culprit (i guess their Google-fu was better than mine)

The SIM900A-model is locked to these regions:

  • China
  • India
  • Singapore
  • Malaysia
  • Thailand
  • Indonesia
  • Cambodia
  • Vietnam
  • Laos
  • Burma
  • Brunei
  • Philippines
  • East Timor

Official documentation is mirrored here: SIM900A Supported MCC List V1.00

Why SIMCOM makes this module, locked to specific regions, i do not know, if you have any idea why, please leave a comment.

User [] had luck upgrading the Firmware on his module – you can read about his findings here – i have not tested the firmware file, as i destroyed my 900A-model in frustration and anger.

14 Responses to “SIM900A regional blocking”

  1. Shamik Says:

    I found your blog when searching for sim900a module layout
    Your module looks great an easier to make single sided board. as it looks
    If you can share your design file it will be great help for me. I bought SIM900A module but still not able to make PCB for it and could not tested for my projects.

  2. Per Jensen Says:

    Hi. You need to be aware, that this board layout is no good for using the module for anything, other than testing the serial communication etc.
    You are aware that the A-model only works in some countries, and cannot be unlocked ?
    The Board-file & Schematic is here:

  3. rizwan Says:

    please tell me that can i use SIM900A in pakistan

  4. Per Jensen Says:

    If you took the time to read the post that you replied to, it does state that Pakistan is not on the list of supported countries.

  5. CodeAsm Says:

    I recieved my sim900A recently and discovered your blog… Damm I wished I saw it earlier.

    BUT please take a look here:

    Maybe with a firmware update it can be fixed. I got my module from DealExtreme and requested help, If they contact the suplier maybe they come with a similair solution and maybe we can unlock our region 😀

  6. Per Jensen Says:


    Unfortunately i destroyed my 900A-model, so i have no way to test it – if i ever got my hands on the firmware file.

    If you get it, please let me know, i can host here on my site too, so we can help others out.

  7. rizwan Says:

    i don’t know why it only work for some specific countries…what are the reasons?i have searched many times on internet but unable to find the reason of locking. If you get the answer in future then please share it with me.Thanks

  8. Mike Says:


    Please be aware that a number of vendors selling SIM900A to buyers the UK, particularly on Ebay..

    Recently I purchased one from ebay UK from a Chinese seller and nowhere on the listing did it state that it wouldn’t work in the UK. They happily allowed me to buy it.

    While it was in transit from China, I carried on reading about the SIM900A and accidentally came across this ebay sellers own store website where they were also selling these modules. Their sales page was a duplicate of their ebay listing word for word except on their website they had the words in bold red font saying “Will not work outside of china”.

    When I contacted them and asked them to clarify why they had not included this information in their ebay listing, they said they knew they wouldn’t work and were very dissapointed that they had even purchased them to sell and offered me a full refund, no questions asked. I notice they didn’t volunteer this information until pressured to do so.

    So please be aware and DON’T buy the SIM900A if you’re in the UK because you’ll just be buying a useless paperweight!

  9. Peter Says:

    I bought a couple of SIM900A mini-modules and they suffered from this UK blocked syndrome. I re-flashed with
    and all is now well. Note that this is for a 64-bit device.
    The firmware and flash file are here

  10. Kostas Says:

    Guys, how do you flash the firmware? Any examples out there?

  11. Per Jensen Says:

    I’ve never tried it, so don’t come asking here. Ask here:

  12. Laurent Says:

    I was able to remove PH-NET PIN restriction on SIM900A 32 bits version.

    I successfully uploaded “1137B09SIM900B32_ST firmware” with “SIM900 Series download Tools Develop 1.9” download tool.

    However after a couple of tests i found this firmware is not able to send emails.

    I think the trick is to try to reflash SIM900A_32 with SIM900B_32 firwmares.

  13. BlogRadar Says:


    Is there any solution to flash the SIM900A module for the North Africa region?

    Thanks in advance!

  14. Per Jensen Says:

    Hi. Sorry for the late answer. I don’t know. Look at some of the other comments here and see what other people did.