ADSL question - those stupid filiters

My question is this; Do I need to have my DSL modem plugged into a filter / splitter in order to get service?

I just ordered standalone DSL service from AT&T (the artist formerly known as bellsouth fast access DSL). I have no voice phone service (aside from my cell phone). It was my understanding that I didn't need to use a filter, unless I planned to use voice phones in the house... but I could be wrong.

I'm using a Westell 6100 that I had in a box from a couple years ago, but I lost all the filters... and the one at Best Buy is only a filter for a phone line, not for the dsl modem... so I couldn't troubleshoot that myself.

The DSL light does not turn solid on the modem... it just sits there and blinks... and the AT&T phone tech (who was very nice, but useless) says there's nothing he can do to help me get it setup until that light stops blinking... aside from send a tech out to the house... I'm assuming the DSL modem just isn't synching with the server (or whatever it connects to).

EDIT: the more I read about these things, the more I'm thinking I need to get a splitter... but the stupid AT&T guy said that I'd just have to buy the whole friggen modem to get one stupid splitter... hmm... your input is appreciated!