This would require between our TA 900 and Linksys PAP2T, which has never been tested... However, you could deploy another TA 900 unit at the remote office (with SIP trunk connection back to the host TA 908e) which would allow you to make & receive calls between the remote TA 900, Host TA 908e, and host ITSP SIP Trunk.
The unoffical short answer is yes. Create a voice user account on the TA900 and set it to connect via SIP. Then setup the PAP2T with the user credentials you configured for the voice user and point it to the public IP on the 908e. If you are using the firewall feature of the Adtran (which we hope you are) allow needed connections from the remote site to the 900. If you need more details let me know.
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