In the first movie, the Nostromo is awakened from a considerable distance by the distress beacon left by the spacecraft. They investigate the craft, things go bad, simple stuff.
The thing is, I don't recall the crew shutting down the transmission, or even knowing how to. Which is important, because if the craft was still broadcasting there's no way the planet could have been settled without knowing about the signal.
My question is, is there some deleted scene or something explaining this?