german | english

Two phones in one - my happier life with a dual SIM adapter

A user report

Studying the rates of various mobile network providers, I found that the combined use of two different phone tariffs (with two SIM cards) would allow for comfortable mobile communication at a reasonable price on my behalf. The tariffs that satisfy my needs the best are "Genion Online" by O2 Germany and "Professional S" by E-Plus and I needed a way to combine the advantages of both.

Beside offering relatively moderate prices for calling mobile phones "Genion Online" provides low rates for (local) land-line calls from home ("homezone") and an additional land-line phone number at which people can call me at low non-wireless rates. "Professional S" by E-Plus on the other hand offers very low rates for calling land-line connections from outside my O2 "homezone". I got a promotional "Professional S" tariff without monthly charge or connection fee (basically free if I don't use it), while my "Genion Online" tariff comes with a monthly charge of about 5 EUR.

Setting up a "national homezone" (requires a third SIM and second phone to be "always on" at home) is something I take into consideration for the future. People would then be able to call me anywhere, anytime at land-line prices.

I currently end up with two SIM cards, but since I am already annoyed by carrying one phone in my hand or pockets when I'm leaving the house, carrying two devices in order to keep my phone costs down is totally out of question. While searching for a better solution I soon stumbled across so-called "dual SIM adapters", which sounded like a promising approach.

Small phones come at a price

My current phone is an M55 by Siemens, which is fairly small and doesn't allow for much (or anything) to be placed between the SIM slot (respectively the back side of the phone) and the battery on top of it. Put a thick piece of paper in between the phone and the battery pack, and the battery (not to mention it's extra cover) won't fit anymore. Thus all kinds of adapters which imply placing two full size SIM cards below the battery will certainly not work with this phone. Other kinds of adapters ("dual SIM covers"), place the SIM cards on top of the battery with a special cover or a battery+cover combination (the SIM cards are connected to the adapter in the SIM slot by cable), at the cost of thickening the phone or replacing the battery with a smaller type. I don't like these, though, as I am not at all interested in replacing my phone's battery (the capacity of which I am satisfied with) with some potentially crappy no-name product. I am also concerned, that the connecting cable might not fit below the battery of the M55.

Violence indeed is a solution

With the above said, I realized that only one solution would probably work for me: both SIM cards would have to fit into the SIM slot at the same time. Of course, the SIM slot of the M55 is in no way designed to fulfill this exotic desire of mine, but some clever freaks other than myself had obviously been dealing with the same issue before and came up with a violent workaround:

If the SIM cards are too large to fit, just cut them to the right size!

When I first read about the so-called "dual ghost SIM adapters", various sellers were offering them in slightly different designs, but with the same functional principle: An adapter, the size of a regular SIM card, hosts two "mini" SIM cards, which you obtain by cropping unnecessary plastic from your regular sized SIM cards.

Additionally the adapter contains electronics for switching between the "mini" SIM cards. Switching between the SIM cards was accomplished by turning the phone off and on (rotationally activating either one of the SIM cards) in all ghost adapters which I initially found.

Not quite what I was looking for

I was not entirely convinced of the solutions I had found so far. First of all, I was hesitant to cut my SIM cards. Theoretically the SIM cards indeed mainly consist of useless plastic and the actual chip inside is tiny small. Practically there is a risk of destroying the SIM card, for example by cropping too much (thus cutting connectors) or due to EM discharge, and having a defective SIM replaced would cost around 12 to 30 EUR. Second: How practicable would the adapter really be? Turning your phone off and on is quite time consuming. Also, ending up with the wrong SIM being active after turning off the phone for reasons other than switching the SIM, would be quite annoying. And finally: the price of all adapters that were available to me seemed a little high.

The ghost adapters didn't seem to be a bad product, but something was missing. So I waited and kept looking for a better solution...

Patience pays off

Soon I stumbled upon a discussion at Telefon-Treff, a web portal focusing on mobile radio. The thread was about a so-called "digital dual SIM adapter", and even though I found "digital" to be quite a stupid buzz-phrase, I followed the discussion. The "digital" news about the adapter was, that switching between the SIM cards was now accomplished by means of a software menu. The way it was done: Sim Application Toolkit (SAT). This was actually quite interesting. Finally someone had made use of the SAT other than by implementing moronic "value-added" services like high-prized SMS services such as ring-tones or weather information.

The adapter was not cheap though (around 35 EUR) and it was a version 1 product: the trimmed SIM cards supposedly had to be fixed inside the adapter with tape and little information was available, whether switching the SIM cards by software might cause problems. But sooner than I could make up my mind, a second generation of the adapter was released, and, a German distributor, offered the adapter at a time-limited discount (23 EUR, shipping included) within the forum.

Digital dual SIM adapter (II) in original package.

For this price I was willing to give it a try, gave up on my concerns regarding the trimming of my SIM cards and placed an order. The adapter was delivered shortly after, with two stencils for cutting the SIM cards and two additional plain plastic adapters, which allow for the trimmed SIMs to be used as regular SIM cards without the dual SIM adapter (just in case...).

A metal cover (known from older "analog" models) had been added to the version 2 adapter in order to fixate the SIM cards inside of the adapter, which gives a much more "professional" impression than having to tape the cards.

Digital dual SIM adapter (II) with metal cover.

Nobody is perfect...

I immediately started practising on some disconnected SIMs, which I still had left over from expired contracts, but I was so (nervously) committed to cutting my first SIM that I didn't keep track of where to cut the diagonal. Quite a stupid amateur mistake!

Stencil for cutting the SIM card

The pieces which I had already cut off had been flying through the room and I couldn't find them. Now I was holding a trimmed rectangular SIM card in my hand an needed to decide on which corner I wanted to cut off. I had no clue. At a chance of 1:4 (1:2 if I had not overseen, that the contacts needed to end up at the bottom) I just cut one of the corners and - the card failed to work. Well done..! I didn't give up, though, cut the next corner, rotated the SIM and - failed again. It was not before the third corner had gone, that the card finally came to life in the dual SIM adapter. I was happy with my results and had got the proof, that being too anxious about cutting the SIM cards is unnecessary.

Excessively trimmed SIM card.

Getting down to business

I (successfully) trimmed another disconnected SIM and an empty prepaid card before I finally touched my "precious" UMTS SIM cards, which, other than my previous targets, were/are actually in use. In my previous attempts I had learned, that cutting the cards with a cardboard cutter was quite challenging, but simple scribing of the outlines with the cutter is a good thing to do, since it noticeably eases cutting the plastic with a regular pair of scissors.

O2 UMTS SIM card prepared for being cropped.

With the outlines scribed into the cards, the scissors follow the lines easily and no excessive force is needed to cut the SIM cards. Notice that some of the golden foil is cropped. This is intentional and no harm is being done to the card.

SIM card after cropping its non-functional plastic parts.

After trimming two SIM cards, both can finally be placed in the digital dual SIM adapter (II) with the golden contacts facing the adapter (if cut correctly, the cards cannot be placed in a wrong way). To keep the SIM cards in place and to protect them, the metal cover, which comes with the adapter, is put in place. At the bottom of the adapter one can see its metal contacts.

Trimmed Sim cards inside of the dual SIM adapter. Cover is being installed.

The adapter can then be inserted into the SIM slot of the mobile phone. The M55's SIM slot is tight, but not too tight for the adapter. The adapter fits well and can be removed without special skills or techniques (some suggest sticky tape to remove stubborn SIM cards from tight SIM slots) by grabbing it at one of the corners next to the chip with your fingernails (see image below). The slot does not completely enclose the SIM card, yet holds it tight and with the battery pushing against the adapter no problems occur regarding lose contacts (inserting paper stripes to increase the pressure, as discussed for some phone models, is not necessary).

Digital dual SIM adapter (II) in a Siemens M55 mobile phone

Put the battery and cover in place, turn on the phone and configure the adapter through the SAT menu. The implementation of the SAT menu varies between different phone models, as the manufacturers can decide exactly where to integrate the menu in their phones. The M55 adds a sub-menu among "extras".

The adapter's SAT menu.The adapter's SAT menu, selection of network.The adapter's SAT menu, speed selection.

The adapter's menu allows to choose between two network lines and offers a third option: "both on-line", which does not mean, that both SIM cards are functional at the same time. It will only make the adapter switch lines in automated intervals. The length of the interval between the automated switching of network lines can be configured by choosing on of the options "express" (frequent switching), "normal" and "slow" (rare switching).

The SAT menus on the original SIM cards (O2 and E-Plus) are superposed and not available anymore. Rumors have it, that the homezone indication in O2's "Genion" tariff will thus not work correctly with the adapter. This is not true for the M55 - the homezone is indicated accurately both by the line "home" in the provider logo and by the little house icon.

Switching lines with the M55 takes about 20 to 30 seconds, beginning with the moment you choose the second line in the menu, ending with the availability of complete functionality on the other line. Check out the video (XviD codec, 28sec. line switch):

Preview image of a video demonstrating switching lines with an M55.(XviD video, 322Kb) download

The phone shortly asks for a SIM, then switches to the start animations. You can immediately enter your pin and wait for the network login to complete. Please notice, that the interface shown in the video is not the standard M55 interface. Several graphics and the layout have been modified in the phone but no patches have been applied to increase the speed of the adapter (regarding aircraft check, read below).

Accessing the SAT menu via your phone's short-keys can further increase your individual comfort. Additionally you can disable the use of PIN numbers (not all providers allow this for each of their SIM cards: with my current O2 and my E-Plus SIMs it can be done, an old (green) O2 Loop SIM won't let it happen) to ease the switching of network lines. Out of security concerns I would not recommend doing this, though.

If the PIN numbers are deactivated, the M55 will ask for an extra confirmation before powering on ("aircraft check" in order to prevent the accidental use of the phone in planes). This can only be removed by means of a software patch, as applied within the following video (XviD codec, 21sec. line switch):

Preview image of a video demonstrating switching lines on an M55 without PINs.(XviD video, 261Kb) download

Some people were wondering, whether it is a problem to distinguish the two network lines in everyday use. As both SIM cards show their own logo and custom logos can be assigned individually to each SIM, you always know, which line you are currently using.


I am quite happy with the adapter. Trimming the SIM cards was not a problem, the adapter hardware and software both appear to be mature and stable and all my needs are satisfied. If you are interested in using more than one SIM in your phone, I recommend trying this adapter.

A possible drawback of the adapter might be its power consumption. I share other users' experience, that the digital dual sim adapter consumes a noticeable amount of energy by itself, which has a negative impact on standby time. I have difficulties with providing an accurate statement on this matter, though: I am living and working in an area with bad mobile network coverage which, in combination with a relatively opulent use of my phone, requires quite frequent recharging of the battery. With this initial condition I am unable to justly evaluate the dual sim adapter's power consumption in detail. Sadly neither manufacturer nor dealers provide any information regarding this issue in the product's specifications. People who set a high value on standby time might want to reconsider their purchase intention. Owners of older dual sim adapters (which lack the SAT implementation) report that their sim adapters have a comparatively lower need of energy than the new digital dual sim adapters do.

Addendum: Where to buy?

The digital dual sim adapter (II) is manufactured by Shenzhen Singularity Industrial Co. Ltd. (China), originally refered to as "third generation dual sim card" (model number: MAI-G-3). It is available from many shops now and you should easily find low priced offers. Some dealers will offer to have your SIM cards punched out instead of having to cut them yourself. Usually this will be done for free (postal charges for sending the SIM cards excluded) or a minor service fee will be charged.

Addendum II: Various Links

Have a look at other topics: