For the SPA-2100, assuming it is connected directly to your Internet connection, you must set the Enable WAN Web Server to yes. This is set in the Router section, Wan Setup tab. You may have to change the default TCP port from 80, particularly if your ISP filters inbound HTTP traffic.

For all other Sipura devices that are likely behind a different router, you will need to enable port forwarding to forward a connection to a specific TCP port on the WAN side to the SPA on the LAN side. Refer to Port Forward which has step-by-step instructions for a number of different routers. Prior to leaving the location of the SPA-2100, make a note of the WAN IP of either the SPA-2100 or the router used between your SPA and the Internet. Then you simply "browse" to that IP in the browser from the remote location. For example, if your WAN IP is x.y.z.w, then you would browse to: http://x.y.z.w. If you change the default port from 80 to, say, 8080 --you might have to do this to get around ISP port filtering--then you browse to: http://x.y.z.w:8080 (or whatever you changed the port to). Note that if your ISP assigns you a WAN IP like 10.x.x.x, 172.16-31.x.x, 169.254.x.x, or 192.168.x.x, then your ISP is assigning you a "private" address and this trick won't work. If you make your SPA's web interface accessible from the web, it is strongly recommended you set both a User level and an Admin-level password. The users are "user" and "admin" respectively (without the quotes of course). You will then need to supply a username and password prior to accessing the SPA's web interface.