Filter/Splitter

DSL/ADSL filters and splitters are often referred to as one and the same
item. But are they - and why the different names?

The reason I ask is because, until today, I used DSL filters for all the
phone connections throughout the house. Today, I bought an ADSL splitter
for a replacement but it doesn't work, i.e., my Speedtouch 330 modem will
not connect through it. Tried it in three different locations.

Have I got a duff splitter or ??

Advice appreciated.

Regards
Joe Steele