Same here...
I do technical field support in medical imaging electronics, and have been on call 24x7 for the past 25+ years, covering all of New England and Long Island alone, except for the 5 years that I tried a different job. That interim job, a national tech support role, meant being tied to a desk and phone for 9 hours of every working day, but when you were off you were off. I couldn't take the tedium, and went back to my prior regional field support job where at least I have flexibility to form my own schedule between support calls, and go out on-site to help the service engineers now and then.
These days, with the recent economic constraints in healthcare, hospitals and clinics are less apt to call in any problems during their off-contract hours, and they are all negotiating fewer contract coverage hours to try and reduce their operating expenses.
Pagers. Remember when they were called "beepers", and it was a status symbol to carry one? Like you were someone important. Boy, did I hate that sound!! t still gives me chills when I hear one go off.
Nobody in our business has pagers anymore. Now they make us all carry a company provided iPhone running AirWatch (look it up), so they can see where we are all the time. They don't publicly admit that this is what they do, but I know first hand that they can and do. If you really want to be off the clock you have to either leave the phone at home or turn it off and put it in one of those mylar RF-proof bags.