I believe Time Warner’s phone service does nothing more than provide you with a standard analog dial tone. I called them in my area and they were very cautious about their service not being VoIP. I suppose this is to avoid some sort of FCC regulation (or taxes).
So, to answer your question, “yes” that is very possible with the TDM400P card. You would need a FXS module to generate dial tone, then connect that line into a phone socket on the wall, then all other phones in your house will be using that FXS line (provided they are on the same line).
Digium’s explanation of FXO and FXS
However, if you want to setup a home-based test system for the Asterisk software, you will only NEED a TDM400P with a FXO module, because you just want to tap into the dial tone provided by Time Warner. From there, you can run SIP hard phones for your extensions, or Soft-Phone software, on any computer at your house.
Then again, if you want an easy way to use existing analog phones, while you puzzle out the wonders of Asterisk, you can get a TDM400P with one FXO and one FXS module ( store.digium.com/product_view.ph … de=RTDM11B )
Now, if $241.00 is too much to drop for just playing around with VoIP, there may be other solutions available. Have you installed Asterisk on a system yet? If so, did you get the test dialer to call the Digium PBX? If so, did you setup a SIP softphone on another computer and dial your asterisk server? I only ask these questions because, for me, these were the building blocks of my interest into VoIP.
Anyway, I hope this helps, and be aware that my information is far from professional.
"off and on asterisk user"