Zte A39 User Manual page 36

seen only in the process of communication and those functions such as Call
waiting, Call keeping, Multiparty need network to support. If you need those
services, please contact your network service provider.
If you couldn't answer the call, press Busy to send busy tone to the caller.
You can do the following operations in the call menu:
Hold/ Retrieve: Keep the current call/Resume the kept call.
Earpiece Volume: Adjust earpiece volume.
Mute: Don't send local voice.
DTMF On/Off： Enable or disable sending DTMF tone.
Answer: Hang on the current call and answer the incoming call.
Busy: Send busy tone to the incoming call in waiting.
Multiparty
Join All Calls: Add the current call to Multiparty.
Hold All Calls: Hang on all calls.
Private: Converse with one side privately and keep the session with the other
one.
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