How to Determine if Android Device has GSM Telephony

public static final String FEATURE_TELEPHONY_GSM was added in API level 7
The device has a GSM telephony stack.
Constant Value: "android.hardware.telephony.gsm"
GSM (Global System for Mobiles)
AT&T and T-Mobile use GSM. Most of the U.S. uses CDMA. Most of the world uses GSM. GSM Phones use removable SIM cards. You can buy unlocked GSM phones and just swap the SIM cards.

1. Get a PackageManager Instance named myPackageManager.

2. Create a Boolean Variable named bolGSMSupported

3. Set the Minimum and Target SDK version  to 7 or greater. 

4. In the onCreate method, add the below code. This will return the telephony ability to a boolean named bolGSMSupported. It will then display a toast displaying the GSM telephony ability of the device to the user.

bolGSMSupported = myPackageManager.hasSystemFeature(PackageManager.FEATURE_TELEPHONY_GSM);
if (bolGSMSupported) {
Toast.makeText(this, "Device has GSM Telephony capability", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(this, "No GSM Telephony capability!", Toast.LENGTH_LONG).show();

5. Compile and run!