Will my device work on Verizon's network without a SIM card?

[totravel]

I've bought a European sim for travel. If I install it before I go, will my iPhone 5c still work on Verizon's cdma network?

[Snn5 · Accepted solution]

Unless I am incorrect:  No, you should install the new SIM when you land or port and power back on.  The SIM, whichever one you have in and running at the time will only operate on the carrier it was designed for.  However, the Verizon SIM might work, but you'd want to make sure you had an International plan before using it in Europe and the European SIM might work here, but that would take away from your International use there.

[totravel]

So I infer that the Verizon iPhone 5c requires a sim in the sim tray and that that sim is both CDMA and GSM. Is that correct?

[Snn5]

The phone requires a SIM to work as a phone or use data over a mobile data connection.  The SIM is not CDMA or GSM, that is up to the hardware in the phone.  Carriers operate on CDMA (Verizon) or GSM (some US carriers like AT&T/T-Mobile and European carriers use GSM.)

[totravel]

Thank you for your reply. I apologize for not getting this all straight. The chipset in the Verizon iPhone 5c works with either CDMA or GSM networks. And there must be a sim in the sim tray, period. So to use the phone here in the US I must have the Verizon sim installed and when I'm abroad I install the sim I bought for travel. Is that correct? So what is on the sim?

[Snn5]

Correct.  A SIM is a Subscriber Information Module.  It provides the network with your information so that your phone is recognized by the provider.  It is the key that unlocks the wonderful world of mobile data and phone calls.

[totravel]

Many thanks!

[Weth]

And just so you know you are not crazy for asking this question, the iPhone 4S had a SIM that was not required for CDMA.  So if you had a 4S your answer would be the opposite.  Starting with iPhone 5, because it had LTE, the SIM is required for all service.