Proper prior notification/training. From my earliest days with my wife when I was in the Army she knew not to call me unless it something important/urgent at my office. This was before cellphones. Even as a Commander, when I had a direct line, she called very infrequently. As cellphones became available, to common, to ubiquitous and I retired and joined the Corporate world, she still didn't call unless it was urgent while I was at work. If she called and I didn't answer, she knew I was unavailable. As texting became more prominent, she continued the no call behavior. She will text and if I don't respond she waits, having the courtesy to realize I am doing something else which requires my attention.
My wife is a classroom elementary school teacher. It is EXTREMELY rare I call her during the day for the very same reasons stated above. She is fully engaged with 20+ nine year olds most of the day. I give her the same courtesy of texting her a "Please call me when you have a moment." if I need to talk, with the understanding it could be a couple of hours before she has the opportunity.
Maybe it is a phenomenon of the younger folks who have never known a world without cellphones, text messaging, email and more, but those of us who came up without them understand the idea of calling, leaving a message and understanding it could be awhile before getting a response is normal rather than instant gratification. Just because we have the capability, does not mean we MUST respond instantly.
On more than one occasion in meetings with my Senior Managers, I've paused and said, "Let's all wait while Bob finishes his urgent text or email and we can resume." I believe employers have a reasonable right to expect people on their payroll to actually be "BE HERE NOW" as it is called my work place. In other words, when you are in meeting or speaking with someone about work related business, give them your full attention. Let emails, texts and yes, even phone calls wait. For that same reason, I hate "Hey you" impromptu pop ins while I am working on something. I believe in concentrating on one thing at a time. If managers need to discuss something more than needing a yes or no on the spot answer, I encourage them to schedule a short meeting time, either in my office or in a conference room. The reason is, so I am not distracted by other work, ringing phones, email etc. If they do that, they know they will have my undivided attention.
It isn't that she isn't important, but about priorities. When you are at work, you need to be focusing on work, especially in an important meeting. As someone else noted, failure to do so could ensure you are never one of the important people...and once you become one, you will have more time to do the other stuff like post in POA at work.
Now, back to work and to answer my wife who texted me 20 minutes ago...