With respect to your question:
1) You asked about connecting to "an ADSL Modem" as opposed to an "ADSL router". Do you envision connecting the ethernet cable from the modem directly to the "10/100SW" switched port on the the ATA188 and then connecting the other port to a PC running Windows XP or other PPPoE software? At the minimum, I think you'll need an inexpensive router (e.g. Cisco 806, ethernet in - ethernet out) between the two devices.
2) With respect to communicating directly without a gatekeeper, I'm not sure how to make that work. There is a service available, however, using a Session Initiation Protocol (SIP) Server and SIP-thru-NAT technology that I'm finding works VERY well for voice communications over the Internet. If you'd like to email me off-line, I'll help with more information and show you how to save money in using it. If you'd care to call, you can experience the voice quality for yourself!
F C Wood
fc@wood.org
832.521.9408
