Can't the iphone 4s be turned on without inserting a sim card?

Iphone4s can be turned on without inserting a sim card, but it can't make phone calls or send text messages. When you are connected to WIFI, you can send iMessage messages and make video calls with other Apple phones via iMessage and FaceTime. Other software industries can use it.

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FaceTime is a built-in video calling software for Apple's iOS and Mac OS X. It can connect to the Internet through wifi or cellular data to realize video calling between two devices equipped with FaceTime. It requires both parties to have an Apple device with FaceTime, an Apple ID and a 3G/4G or wifi network with Internet access.

IMessage is an instant messaging software launched by Apple, which can send short messages, videos and so on. It has high security. IMessage is different from SMS/MMS service of operators. Users only need the data support of WiFi or 3G network to complete communication. IMessage uses the new message reminder system of iOS and Mac os, which can directly push information to the other party's screen, regardless of whether the other party is in the game or locked. If both parties are using iMessage, you can even see the state of each other's speech.