I"m not sure how it works where you are but I can tell you here in the states that I know you should have a caller. I do know of one or two people that don't use a caller though that fly in FAI class. Sportsman though, I believe you should always use a caller. It helps calm the nerves. I think if you fly at the nats a caller is required . Not sure on this though. Anyway. As far as regular contests are concerned here in the states, a callers function is to provide you with the manuevers by speaking them to you in a calm tone. The judges don't have to here them, but some judges prefer to. It makes it easier for them to score if they don't have to look away from your flight to read what manuever is next. You do not have to say start or end to manuevers. Although you do at times have to tell them entering or exiting the box when you are not in a turnaround manuever... Hope this helps, good luck to ya!!!!! Chris