Long call is you answer phone 24 hours a day. When called you can be asked to show for an assigned trip in not less than 13 hours. You're released from on call to rest at the time of assignment.
Short call is a 14 hour period to answer phone with 10 hours not, each day. If called you can be asked to be at airport within 2 1/2 hours to be off the gate within 3 1/2 hours. Your FAA duty day starts at the beginning of the on call period.
That's the basics. Usually they'll give you more time. For instance you're on short call and they'll call you at 1600 and assign you an 8 am show and release you from being on call until then. There are many variations to what they can do (to say the least).
As I understand it, under the new regs, that will all go away? Apparently, all time on reserve will count as duty time as soon as you start your reserve. Anybody here well versed in the new regs?