I worked for a 24x7 manufacturing operation for 7 years where I had to be part of a rotating call schedule. When I started off-hours calls were limited to problems that meant we could not produce or ship production. By the time I left it included times when someone could not get on the internet. I actually got a call 7 am on a Sunday from the corporate controller because he could not get his email. I fixed it, but I also told him there was no good reason he should be working at 7am on Sunday and that I shouldn't have to either since the mill was still running fine.