The Do Not Disturb (DND) feature will temporarily prevent your softphone from receiving calls. You are still able to place outbound calls while DND is enabled. If you have the softphone app installed on multiple devices, each device has a unique DND status. This means that if you set your mobile softphone to DND, you desktop will still ring.
To enable DND, click the moon icon near the lower left of the softphone window:
The icon will change to be solid, and you will see a notice that DND is now enabled at the bottom of the window:
To turn DND off, simply click the moon icon again. The icon acts as a toggle.