There is a new feature in the latest iOS8 system, which is called "continuous intercommunication", which allows the iPhone to communicate with iPad or Mac computers.
Of course, if you want your iPad to use an iPhone to make a phone call, you need to use the same account, that is, the same Apple ID, to log on to the Facetime on the two devices. Find the Facetime option in the Settings list and log on to the iPhone and iPad with your account. In addition, the "iPhone mobile network call" in Facetime must be enabled.
When iPad and iPhone use the same account to log on to Facetime
The second condition must be met, that is, it must be in the same wireless network, such as connecting your own wireless LAN.
Third, you also need to enable Bluetooth for both the iPad and iPhone, and only these models can detect each other: iPhone 5 or newer models, iPad (fourth generation) iPad Air, iPad mini, and iPad mini with Retina Display. Therefore, no other devices can use the iPhone to make phone calls.
After everything is ready, you can try to call the iPhone on the iPad. It can directly call contacts in the iPhone or other phone numbers. Of course, if there is a call to the iPhone, the iPad will display the same, you can answer the call between two devices. As shown in the following figure, after opening Facetime on the iPad, select the "audio" column to make a call.
The following figure shows a screenshot of an iPhone call on the iPad, as shown in the following figure.
You can also see that the Mac can also use the iPhone to make phone calls, as shown in the figure below.
This new function in iOS8 is very convenient and practical. When we are at home or in a public room, we can use other devices to make calls without the iPhone. If the phone call function cannot be enabled between multiple devices, check whether the iCloud account is correctly set, and check whether the account must be connected to the same wireless network. In addition, check whether your iPad or iPhone supports "continuous intercommunication". You can view the list of devices that support it below.