The Fair Labor Standards Act requires an employer to pay overtime (time and a half) for hours in excess of forty hours per week. Certain kinds of employees are exempt from this requirement. For example, managerial employees (those whose main job is the supervision of other employees) fall within the executive exemption. Human resource managers usually fall within the administrative exemption. Most exemptions require that the employee be paid a salary rather than an hourly wage, but being salaried does not make you an exempt employee. If you are not exempt, you are entitled to overtime even if you are salaried. However, calculating the overtime is not as simple as you might think. For example, suppose you are a non-exempt salaried employee making $500.00 per week. If you work 40 hours one week, your effective hourly rate for that week is $12.50 per hour, but since you didn't work more than 40 hours, you get only your salary. The following week you work an extra ten hours, for a total of 50 hours. Your effective hourly rate for that week is only $10 per hour ($500/50 hours). But you are entitled to time and a half for the last ten hours. Your salary covers the time ($10 per hour) so you are entitled to another half ($5 per hour) for the extra ten hours. So in that week you would be entitled to an extra $50.00 in overtime pay.
The idea of being "on call" raises a tricky question that is difficult to answer in some cases. If you are "on call," the question is whether you are "employed to wait" or "waiting to be employed." In other words, if your only responsibility is to keep your cell phone in case you are needed, you are not entitled to be compensated for extra hours unless you are actually called. On the other hand, if you are required to stay at the worksite, you are considered working even if you don't have anything to do. Most situations fall somewhere in between these extremes. For example, if you have to remain within a ten mile drive to the worksite, but you are free to shop, go to a movie or engage in other personal pursuits subject to being interrupted with an emergency call to return to work, you are not entitled to count the hours you are "on call" simply because your travel is somewhat restricted. If you are an exempt employee you are not entitled to be paid overtime, so none of this matters. To determine if you are truly an exempt employee, you should contact an attorney or the U.S. Department of Labor.