KR,
Dont use the A200 it is terrible. There is a company called QTelNet that makes gateways that take care of the IP address changing for you without the need of a gatekeeper and you wont have to worry about posting your IP address when it changes.. It is a behind the scene messaging system. There are 2 port FXO and 2 port FXS. As per a previous post you can pick them up online here : http://www.atacomm.com
Hope this helps.