Can I use more than one HomePlug on the same electrical system?

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http://serverfault.com – I'm trying to wire up an old college office (with 3 rooms) that has thick cement walls. Running ethernet is painful, and wifi can't break through the concrete. Can I use more than one HomePlug to connect these 3 rooms to the main switch (which would have its own plug) My thought is that the ethernet will broadcast the signal properly and that I don't have to worry about conflicts because the ethernet will handle the collisions appropriately. (HowTos)