Yes the TotalAccess 904 will work fine for this.
Each side will convert TDM to VoIP passing the voice traffic over the VPN.
The main difference is that now you will have a full 23 channels instead of four.
Please post if you have any config questions.
Thanks for the response.
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I have submitted another discussion needing some support on this. I have some configs. I could forward you. I am able to see the PRI on each side come up but the D-channels don't come up and I don't see any SIP registrations.
Not sure that the configs I am using are right for this type of application.