Your thoughts?

SIMply amazing?

Usually, with Functional Friday, I talk about something that is here in Japan that you might be able to use. However, today, I want to talk about something that we don’t deal with at all here in Japan, but seems to becoming usual in the rest of the world. That thing is the SIM card.

So, what the hell is a SIM card?

Photo from


SIM stands for Subscriber Identity Module and it is the way the phone company tells who owns a phone and who to charge. has a good primer on SIM cards here.

In Japan, we don’t do much with SIM cards. This is because Japan has generally used a CDMA (Code Division Multiple Access) network, where the phone number and the handset information are saved on the phone itself. This is usually the case where the company subsidizes the handset to get you to pay your money through your data plan. As Japan moves to an LTE network (‘Long Term Evolution’), phones that use that network need to have a SIM card. But because of the presence of the CDMA network, phones in Japan are ‘locked’, which means that you can’t exchange SIM cards.

However, in countries where the phone company or companies do not subsidize the purchase of a handset it is a very different story. These countries tend to use a GSM (Global System for Mobile communication) My recent trip to Kyrgyz and my trips to Vietnam have shown me that if you have an ‘unlocked’ phone, you can simply buy a SIM at the airport or the electronic shop and voilà, you have a phone.

This is all more than a bit confusing, or, as this excellent discussion of acronyms notes, “If you wanted clarity, I’m sorry that just doesn’t come with this subject.  It’s a chaotic subject in a very chaotic time.”

You may have seen discussions about ‘unlocking’ phones. While I’m still investigating this, Softbank only seems to unlock phones in very rare cases, while it seems to be possible to do so with AU. However, my hope is to pick up an older iphone, maybe a 4 or 4S, have that unlocked and then use that as my overseas phone.

imagesIf you are able to unlock your phone, you can then swap out SIMs. However, as
the image shows, there are different sizes of SIMs. SIM shops will have SIM cutters to make the larger smaller and SIM adapters, which allow the smaller SIM to be held in place in a larger slot.

If you’ve done it, let me know how it went. If I am able to get this sorted out, I will report on it in another FF.

1 thought on “SIMply amazing?”

  1. Joe,

    Thanks for the concise explanation. I always wondered how those SIM thingys worked. Looks like I’ll be hanging on to my 4s for a while. Looking forward to an update. “SIM cutters”….sounds very McGyver-ersque. (80s TV show reference).

Leave a Reply