I heard some of these systems are illegal to use in the States, how can I tell which one to purchase to avoid getting into trouble?
You should always make sure that the included transmitter in the system has an FCC ID printed somewhere on the device, usually on a sticker in the back. This is a code given by the FCC to devices that comply with all their requirements for FM capable products. Many cheap systems online lack this, and therefore are illegal to use. We recommend the Enersound bundles, which feature an FCC ID on their transmitters.