SMS sending
Allow all users, allow admins, or no. A weekday start and end grid appears when the choice is not Allow all users.
Calling
Calling uses the same three choices. The calling grid is also shown when Inbound Calls is set to skip people outside hours.
What each choice does
Allow all users means the window does not block that channel. Allow admins lets administrators act outside the window. No means the action waits for the next window.