Mobile phones, services and applications. PCs, PDAs, Wi-Fi, Bluetooth, Internet, gadgets, electronics, photography. A technology-life journal ... Relaxed prose, sometimes witty, sometimes funny, reflective and insightful. Short and sweet. Filipino.

Thursday, February 03, 2005

All that SIMs, all that Matters

This is a long overdue article. I've been wanting to talk about how to deal with having different cellphone numbers on just one cellphone.

I believe this dilemma escalated for a million more cellphone subscribers when Sun introduced its 24/7 Call and Text Unlimited service. As I discussed in a previous post about Sun, we expected more people to acquire and maintain a second SIM apart from their primary SIM. I sometimes refer to my second SIM (my Sun SIM) as a "part-time" SIM.

Two SIMs, one cellphone ... (as my classmate Kalayar would say)... "What to do??!!"

Well, here are a couple of options: MultiSIM, Dual SIM and Micro Dual SIM. Let me share some stuff I know about these SIM tricks...

One telco calls it Multi-Line SIM, the other calls it Multi-SIM (or something like that). Basically, it's a service the telcos offer to their post-paid subscribers. You can have two cellphone numbers (from the same telco) "joined" into just one SIM. Your second line could be another post-paid SIM or could be a pre-paid SIM.

You'll be able to send and receive SMS messages from both numbers at the same time. You'll also be able to conduct incoming and outgoing calls using either number. You'll just need to switch between line 1 and line 2.

How is this useful? This comes in handy if you want to separate, say for example, your business calls/texts from your personal calls/text. You can use SIM1 for business, and SIM2 for personal calls. Or, if you're the naughty type, use SIM1 for one better half and SIM2 for the other better half. (If they're both better halves, doesn't that make you a mediocre nothingness?).

Now here's the mystery for me (maybe some visitors could clarify this for me). The telcos say they can join up to 5 cellphone numbers into one MultiSIM. Hmmm..... I don't know how that works because I've never seen a "line 3" in any cellphone. My guess is they have an STK (SIM Toolkit) selector menu that shifts the user from one SIM to the other.

Now isn't that a complicated life?

Limitation of the MultiSIM service of the telcos: they'll let you have have MultiSIM for SIMs from the same telco only. Why the heck would they help you use a competitor's SIM, right? But, why the heck would *I* need two SIMs from the same telco in one MultiSIM. I'd find it handy if I can put my Addict Mobile SIM, my Sun SIM and my soon to come TM (Touch Mobile) SIM in one MultiSIM. *That* would be useful.

Multi-SIM ng ma-abilidad

If you're the shady kind of character, you'll be able to find technicians who will ... uh ... "make a way" (gawan ng paraan) to put together SIMs from different telcos into just one SIM. That will require a SIM burner that, I hear, is a very expensive piece of equipment. I hear SIM burning services cost more than P500. This, I'm just recalling from some old discussions over ph-cyberview. Search the list's archive if you wish.

Dual SIM
borrowed without permissionThis is the corny solution to a 2SIM 1Phone dilemma. Basically, there's a gadget that will house 2 SIMs. With a little electronics and acrobatics, the SIMs are "connected" to the phone one at a time. The SIM housing is a little cumbersome and either rests inside the casing between the phone's battery and the back casing. There's a worse version of the Dual SIM where the SIM housing is *outside* the casing. Un-cool.

To switch between the two SIMs, there's a series of keys that need to be pressed, sometimes it requires turning off the phone and then turning it on again.

Dual SIM housings come in different shapes and sizes and fit in to particular cellphone models. I think you can get them for around P150-P400 at greenhills depending on your cellphone model.

Micro-Dual SIM
This is what I found useful for my needs. The Micro-Dual SIM. A picture paints a thousand words. An animated image paints a thousand more pixels. So here are a couple of animate gifs borrowed without permission from, . Visit their site to purchase Micro-Dual SIMs. borrowed without permission from

Sayang, I couldn't find the animated image that shows how the 2 SIMs will fit into the micro-dual SIM. But here's an alternative illustration:

I purchased mine at Greenhills, 2nd flr bridgeway. Try contacting them: 0919-6302000 or 725-0716. Back then (Nov 2004) the retail price was P350-P400. They have a vice-grip that will punch out your SIMs so that it fits snugly inside the Micro-Dual SIM metal housing.

The up-side: no cumbersome SIM housing. The Micro-Dual SIM housing is the same dimension as the ordinary SIM (except it's a fraction of a millimeter thicker). Thus, it fits in almost 95% of cellphones in the market. (For some reason, I hear it doesn't work well with O2XDAs.)

The down-side: It can be erratic, sometimes. Let me share my experience. In my excitement to tell friends about the Micro-Dual SIM, I had the tendency to take out the device and show them the two cut-out SIMs. Then, when I'd put it back, it wouldn't work perfectly in the first try. Thus, the tip I've seen in airfagev forums is: Once it works well on your cellphone, don't take it out anymore.

To switch between two SIMs, I would just put Airplane mode On/Off. This is just like removing the cellphone signal then restoring it.

For some reason, I've had experiences where I thought I was on my Smart SIM, but next time I look, I'm on my Sun SIM. I figured this happens in some instances when the signal is lost because of cellphone signal deadspots.

Another thing I've observed is that the Micro-Dual SIM eats up some of my battery's standby time. This is bad for me considering that my SmartPhone, Brosia, has a limited battery standby time of around 14-18 hours only. Nabawasan pa yan because of the Micro-Dual SIM. Furthermore, I have the impression that the Smart signal requires more battery power to sustain compared to the Sun signal. I say this because when I'm running low on battery, my cellphone turns off once I shift to Smart but still could turn on if I'm on Sun. This, I believe, has something to do with the frequencies that Smart and Sun use -- 1800/800 MHz for Smart and 800MHz for Sun. (Hope I got my figures right).

Edong's Dream SIM:

My wants are simple - I want to have my Addict Mobile SIM and Sun SIM (or later my TM SIM) working all at the same time in just one cellphone allowing me to send/receive text of any SIM anytime. And I'd like to do outgoing/incoming calls through any of SIMs I choose. I'll use the SIM that offers the best rates whether I'm calling, texting or connecting to GPRS.

While I'm at it, I'd also wish to have a SIM that will allow me to make calls from my PLDT landline using my cellphone. Is that too difficult?


In a nutshell:
  • Use a MultiSIM if you want two or more cellphone numbers from the *same* telco in just one SIM
  • Get a MultiSIM burned for you if you have SIMs from different telcos (this service is not common).
  • Use a Micro-Dual SIM if you're willing to cut out your two SIMs and can deal with having just one cellphone number available at a time.
  • Use a cumbersome DualSIM if you're anti-cool and have no other choice.

- Edwin

I'd like to hear your experiences with similar devices. Do share!


  • At 10:51 am, Blogger Alvin said…

    i love this line:

    Or, if you're the naughty type, use SIM1 for one better half and SIM2 for the other better half. (If they're both better halves, doesn't that make you a mediocre nothingness?).

    anyway, this is really some cool stuff, esp the microdual...right now, im very much contented with my postpaid sim...pondering on a second SIM after reading this post...kudos Ka Ed!

  • At 5:26 pm, Blogger Airwind said…

    this one i need my friend!!!!! coz im having problem removing my sun sim whenever i want too call somebody from a different telco. then putting it back again... (ope you understang what i mean. im so stressed at work) tnx for the tip!!!

  • At 7:37 pm, Anonymous Anonymous said…


    there was a time when I wished I had one cell phone number for 2 cell phones.

    One was for surfing / sending emails.

    the other was for just making calls, or texting while driving. (grin)

    One with camera. one with no camera that I can use to enter the casino or some manufacturing companies thatr forbades cell phones with cameras (grin)...

    wilson ng

  • At 9:53 am, Blogger Edwin "ka edong" said…

    > there was a time when I wished I had one cell phone number for 2 cell phones.

    That's a "Wilson's Dreams" SIM ;-)

    I too see how that would be practical. I know a SIM clone can be made from an original (from a discussion on ph-cyberview). But given the current technologies, I don't know how that can be made to work on the telco network.

    I remember upgrading my old post-paid globe SIM. What globe did was issue a 128K SIM. I was told that within 24 hours, my old 64K SIM would loose its signal. At that point, I can slip in my 128K SIM and it would work perfectly then on. But the SIMs did *not* work at the *same* time.

    Imagine your two phones with the same number being separated - one in Cebu, one in Manila. If there are two identical SIMs (clones), how will the telco network know where to route a call? When a friend calls your number, which phone will ring? Both? Baka malito ung network! ;-p

    I guess the setup would be - Two phones, two SIMs with the same number, one is a master SIM, one is a slave SIM. The master SIM does both incoming and outgoing tasks (calls, text etc.) and the slave SIM allows only outgoing tasks (outgoing calls, outgoing text, outgoing GPRS connections).

    pwede ...


  • At 7:46 pm, Anonymous Anonymous said…

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  • At 4:24 pm, Anonymous another mobile geek said…

    Nice article. Check out my experience with a dual sim ghost adapter, if you like:

    It includes video files showing online switching of network lines.

    It might be useful information for people who consider buying a twin adapter since it gives you a good impression of how these actually work.

  • At 11:31 pm, Blogger Edwin "ka edong" said…

    Guten tag, C.S. (another mobile geek)!

    Hey, thanks for your contribution. You ARE another mobile geek!

    I couldn't play your AVI's though. Don't worry, "it's me, not you." My media player needs some codecs to play your avi's.

    When I first saw your site, i thought it was the site that had the animated gifs that showed how the two sims fit in the dual-sim.

    your story shows how patience (and violence! ;-) ) work.

    Keep it up, mobile geek!


    ka edong

  • At 11:32 pm, Blogger Edwin "ka edong" said…

    hot linking C.S.'s article: Two phones in one - my happier life with a dual SIM adapter

    -- ka edong


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