[RFI] CAT 3 Cable?

[Eric Rosenberg]

In trying to calm down the telephone RFI problem in my old house, the
K-COM folks suggested I replace the old, solid, 4-conductor wire with CAT
3 cable. 

I'd never heard of CAT3, only CAT 5, and am wondering what it is and
whether it's worth the effort.  The reality of my situation (an old house
with plater and lathing walls) is that I can only replace some of the
wiring, not all of it. 

Thanks in advance, 

Eric W3DQ
Washington, DC