AASTRA DT4x2 for MX-ONE User Guide EN - Manual (Page 58)

During Calls
DT412/DT422/DT432 58
Mute microphone
To mute the microphone during an ongoing conversation:
Press the Mute key at the right side of the phone to turn the
microphone off.
The microphone is disconnected and the caller will not hear an
ongoing conversation or environmental noises. The text Muted is
shown in the display when the microphone is off during a call.
Press the Mute key again to turn the microphone on.
Note: It is advised to use this feature instead of putting a
call on hold. A call on hold may be diverted to your operator,
directly or after some time.
Inquiry
You have an ongoing conversation and you would like to make an
Inquiry to an internal or external party.
R
Press (see display).
Dial tone. The first call is put on hold. å
Call the third party.
When the third party answers, you can switch between the calls
(Refer Back), transfer the call, create a Conference and end one of
the calls.
R
Press to end the Inquiry call (see display).
The third party is disconnected.
ж ж
Press to return to the first party.
Refer Back 2
Press to Refer Back to the other party.
The party you talked to is put on hold, the other party is connected.
Note: Sweden press R (see display).