Grandstream’s HT series of Analog Telephone Adapters (ATAs) offer a ton of features at an affordable price point. They are trusted and deployed by some of the world's largest service providers. The HT502 is a dual-port FXS, with 10/100 Mbps ethernet and no router. It supports 2 SIP accounts.
Update to the latest firmware for your HT502 before connecting to our service. You can download the current production release from the link above. Once downloaded, you'll navigate to "Advanced Settings" and click the "Upload from Local Directory" button. Select the file you downloaded from Grandstream' website, and then click "Apply" once this has completed your device will reboot. You can then move on to the steps below.
Select "FXS Port 1" from the primary menu, and and configure the following options for your SIP Registration:
Primary SIP Server: sip.t38fax.com:5080 help
Outbound Proxy: sip.t38fax.com:5080 help
NAT Traversal: Keep-Alive
SIP User ID: SIP Username help
Authenticate Password: SIP Password help
Local SIP Port: 5080 ( Not pictured below )
Scroll down and configure the following options:
Allow Incoming Packets from SIP Proxy Only: Yes
Finally, configure the following T.38 specific options further down the screen:
Fax Mode: T.38
Fax Tone Detection Mode: Callee (Added as of version 184.108.40.206)
Finally, configure your fax machine to work properly with your Power-T.38 SIP Trunk. Review our Recommended Fax Machine Settings for details.