How to call back the phone that BBK landline just answered?

Press the callback key to call back the phone you just answered. According to the relevant public information, if the landline wants to call back, it can choose to click the call back button in the upper left corner, or press the green call back button to automatically call back. The landline is one of the important modern communication means. The microphone in the telephone modulates the current and voltage on the telephone line through the vibration of the sound, that is, it converts the sound into a voltage signal and transmits it to the other end of the telephone through the telephone line.