"God bless the child who's got his own!"
Having received no reply, I managed to discover that the NT-1 network interface has only two (2) S/T ports and that the Adtran Express 3000 or 3010 will not work, as it has but one 2 U port.
The answer to the question is to purchase the Adtran Express 3110, which has an S/T port.. The 3110 has two POTS ports for phone or fax. Easier said than done. But, that's the answer.
Now, speaking of the NT-1, I purchased the Eicon Networks NT-1 device. It cost around $150. It has two S/T ports.
If you're using the AudioTX Communicator in the United States, the product performs well. But, keep the following clearly in mind . . .
I know that some of us have become accustomed to putting hypens in after the area code and between the number and the number pre-fix. Do not do that. This stuff is pretty techie and not oriented toward the general consumer.
The AMV Friitz/BT Speedway ISDN card has no intelligence built into it, nor does the driver deployed by Windows that must be used in the U.S., to strip out non-numeric characters.
The result is the SPID's are not sent to the switch and no ISDN circuit is established or possible if hyphens or parens appear in the numbers.
Please note: when you configure the ISDN card the ISDN numbers and the SPIDS must be entered without any hypnhens or parens.
That's not the case with AudioTX Communicator. It has intelligence to strip (ignore) any hyphens between numbers.
Lastly, make sure the correct protocol is specified in the ISDN card. The switch may be AT & T and designated ESS5 National. That's hardware. The actual protocol may be NI-1, which can run on ESS5 National (hardware). That was the case with SBC's circuit. The tech who did the install said the protocol was ESS5 -- which it was and is not.
Enjoy.
CC