Am I entitled to compensation for being "On-Call", and is my travel time spent returning to my facility to cover an emergency call in considered work?

I am an hourly paid Electrical Controls Technician at my facility. My manager has instituted a weekend rotating "On call" schedule for my depart to cover problems and provide assistance to our maintenance crews. My normally scheduled hours are, Monday-Friday, 7am-4:30pm. At this point all we have been told is that on our assigned weekend we are required to respond to any and all calls at any time during the entire weekend. And, that the only compensation is pay for hours worked. We have not been given any restrictions regarding response time, alcohol use while on call, or anything like that yet. But I am sure there are certain expectations that he has as to how soon we are able to respond once we are called. The second aspect of this; Is my time spent commuting to and from work responding to an emergency call in, time I should be paid for, or something I should get to expense on a per mile basis?