Thanks Mic and Jez for their sharing. I don't really want to make my own modem, what I want is an alternative of socket modem. It would be the worst case if I have to make my own modem and go through all the type approvals examination. I found that all the companies that build socket modem are from the west, is there any one know if there is company in the fast east building the same thing? I suspect the price will be lower than their counter part in the west.