iOS Developer Library


Core Telephony Framework Reference



Use the Core Telephony framework to obtain information about a user’s home cellular service provider—that is, the provider with whom the user has an account. Carriers can use this information to write applications that provide services only for their own subscribers. You can also use this framework to obtain information about current cellular calls.

A CTCarrier object gives you information about the user’s cellular service provider, such as whether it allows use of VoIP (Voice over Internet Protocol) on its network. A CTCall object gives you information about a current call, including a unique identifier and state information—dialing, incoming, connected, or disconnected.



NSObject is the root class of most Objective-C class hierarchies.


Use a cellular call’s CTCall object to obtain an identifier for the call and to determine the call’s state.


Use the CTCallCenter class to obtain a list of current cellular calls, and to respond to state changes for calls such as from a dialing state to a connected state.


Use the CTCarrier class to obtain information about the user’s home cellular service provider, such as its unique identifier and whether or not it allows VoIP (Voice over Internet Protocol) calls on its network.


The CTSubscriber object provides cellular network subscriber information.



Use the CTTelephonyNetworkInfo class to respond to changes in the user’s cellular service provider.