First, you need to establish a connection by placing a phone call, but after the connection is in place, you can communicate bidirectionally with each other.

首先，你需要设置一个话机以建立一个连接，但当连接正确建立后，你就可以与另一方进行双向的通信。

youdao

Voice activation is perfect for placing a call; opening the flip lid on a phone is probably the most effective way of answering it (or again using voice activation for hands-free use).

语音激活来打电话就非常理想，打开翻盖手机的盖子来接电话无疑也是最有效的接电话的方式之一，或者用语音激活免提功能。

youdao

The two were close and Mr. Jobs trusted Mr. Cue to negotiate partnerships, placing a phone call to a media chief only when it was required to seal the deal.

WSJ: Eddy Cue: Apple's Rising Mr. Fix-It