TDAmeritrade does not provide direct routing options for a long time now. According to them, their management has decided against it.
Call Scottrade and ask - or do they have a demo on their website? I've never used the product so I can't answer.
You have an option to route your order with TD or TOS. You do not get credit for adding Liq. though. Rick
Rick, In TDAmeritrade's web-site they still have kept the misleading options for INET and ARCA. However, it does not actually go to INET or ARCA as it was used to; it now goes to the auto-router. The decision has been made a while ago.
For direct routing on options and stocks go to Interactive Brokers. They have the best execution statistics of any online broker for both stocks and options (http://www.interactivebrokers.com/en/p.php?f=smartRouting) They are also the least expensive broker I know of for stocks, options, FX, and futures. To open an account with them just click on this link and it only takes 5 minutes to fill out their newly redeveloped online app: https://www.interactivebrokers.com/Universal/servlet/formWelcome?p=100&atype=IT&ibsrp=139