The MC74 makes it easy to put calls on hold or take them off hold. This article offers an overview of how to use hold to stop audio transmission and reception to an active call and return back to it at a later time.
While in an active call, you can pause audio transmission to and from the call by pressing the Hold button at the bottom of the screen.
The phone screen will indicate that the call is held with a dark blue/black background color on the call and the Hold button. To take the call off hold, tap the Hold button again.
When there are multiple calls ongoing, only one can be active at one time. When the screen for one ongoing call is active, the other calls will be placed on hold.
If you are looking to combine the ongoing calls into an ad-hoc conference, you can follow the steps described in Ad-hoc Conference.
To return to a held call and place the current active call on hold, tap anywhere within the dark blue/black background of the held call.
To place the active call on hold as well, tap the Hold button in the active call. This will not change the hold status of any other ongoing calls.