When I charted to TTA, It just meant that we used condoms until Ovulation was confirmed.
Charting to TTA can totally be done, but since my cycles are a little off (well, they're really off now but not as much as pre-baby), we didn't want to abstain that long, so condoms it was.
ETA: You have to be REALLY confident in your past cycles O dates to do just charting. OPKs won't help because likely they'll tell you too late that you were fertile and an oops is more likely. If you're TTA, but are okay conceiving, then you can be a little less careful.