thanks for your help.
newbie, about the ebay link, you said that that one has a crystal which the one on the Arduino site doesn't have.
what is it uses for? timing?
is that essential?
is that board on that ebay link a genuine Arduino?
if so, how come it's not on the Arduino hardware page?
http://cgi.ebay.com/Arduino-MEGA2560-ATMEGA2560-ATMEGA8U2-USB-Cable-/260725146026?pt=LH_DefaultDomain_0&hash=item3cb46e01aa
is it preferable to order that one (the one on ebay) instead of the one you see on the Arduino hardware page? (it's also the cheapest price I saw till now...)
Graynomad, you mean that because the cables are spread all over the house over too long distances, I will have problems with the operation?
how can I solve it using an RS-485?
Thanks!