Hi,
Do you dial out and get the ringing of the FXS line and not the FXO? if so, I had the same problem. The solution is to set up to External Line to point to the proper TCP port. The default on the HT-488 for the FXO is 5062 and the FXS is 5060. Use the 5062 to use the FXO for Dialing. The syntax in the Server field is 192.168.250.52:5062. My HT-488 is using IP address 192.168.250.51, and you can substitute your address. I hope this helps.
Also, your HT-488 only supports two stage dialing as it comes from the factory. Which means that you will get your first dial tone when you first pick up your phone, then you dial your number, then you will get your second dial tone and your will have to dial your number again. This practice is quite common for many manufactures. Single stage dialing, which what I wanted and need is being tested by Grandstream engineering as we speak. So, for the short time you will be able to use your HT-488 ony in two stage dialing.
Best regards,
Todd Simpson
IT Consultant / Client Support
Interconnectix
(Solutions for your Connected World)