Can my “au iPhone 4S” use the GSM network at the outside of Japan?

Recently, I feel that iPhone 4S users rapidly have been increasing around me.
Well, it was very hard to search the information about the subject, so I would like to inform here.
This is the information based on the au support Center and au web site. 

• au iPhone 4S is supporting the network both of GSM and global CDMA.

However, there is the following restriction.

Priority is GSM network. 

This is the restriction for au iPhone 4S by Apple co.
au iPhone 4S cannot manually choice  the carriers (Softbank iPhone can choice)
In other words,

• In GSM network area, au iPhone 4S automatically selects GSM network.

In case of the outside of GSM network area and global CDMA area, au iPhone 4S will select global CDMA by setting up the following setting (Basically, global CDMA is disabled).

How to enable/use global CDMA

* In GSM network area, au iPhone 4S automatically selects GMS network.

1. Tap on “Settings” –> “General” –> “Network”.
2. Enable “Roaming” and enable “Global CDMA”.

Of course, you don’t need to change the setting in GSM network areas.

Premise Document above information

Please see  “Charges” section in the following au web site.

• Overseas Double-teigaku：http://www.au.kddi.com/english/service/kokusai/packet/index.html

Smartphone: Global Passport CMDA/GSM.
However, you may suspect that au iPhone 4S does not go into the category of a smart phone.
O. K. I provide more information.  Please see the end of “Carriers” section.

• [4] These carriers provide only a UMTS network, so a UMTS-compatible
  device (IS11PT, EIS01PT, IS12S, IS12M, iPhone 4S) is required in order
  to use these carriers.

UMTS network involves both of GSM and global CDMA. Therefore, au iPhone 4S can use GSM network.

9th April, 2012  Chief of Information Processing Office: Kitani.