Though Eric Kaufman got the answer straight, I just wanna pitch in on the following statement:
Some say I should not bring headphones at all (and that they might actually be banned,
I'm just reading about it on running websites.)
As a seasoned runner I've ran in different countries and did different kind of races (track, trail, road,...).
Most races are run on a closed circuit (e.g. no regular traffic on the road). Hence there is no real threat for the runner. The roads itself are wide enough for other runners to pass you. So therefor there is no risk for you (as runner) to wear headphones and to be absent about whats happening behind/around you.
Trail-runs however are something entirely different. Some are indeed closed circuit or have volunteers keeping the road open for you to cross it. However there are as many trails where the roads are not closed for the regular traffic. Or where the tracks are very narrow and slower runners might hold up the faster runners.
Therefor the organisations often demand the runners to avoid using headphones for their safety and the enjoyment for all runners.In those cases you have to be aware of your surroundings! Because nobody likes to get run over, attacked by a wild animal or get hold up behind an other runner.