I recently picked up a Uniden BC895XLT.  This is a great TrunkTracker radio
out of the box, but I  wanted to add a discriminator output and use it's
computer control.  It took a while to find all the information, so I have
created this document to put it all in one place.
For the computer control cable I used a 9 pin RS-232 interface on one and
for the other end I used the connector from a cable that is used to attach a
CD ROM drive to a sound card.  It is a flat 4 pin female connector.  The
BC895 has an interface with 5 pins, but since pins 1 - 5, and  pins 2 - 4
are connected, only a 4 interface connector is needed.  I don't know if Rat
shack has this connector, but any kind of computer parts place should.

These 2 links will help you build the cable.

http://gary.burkett.org/BC895XLT_Cable.html
http://www.futurescanning.com/895cable.htm

The discriminator is easy to install since the radio has plenty of room
inside the case.  I mounted a mini plug connector inside and used the "Greg
Knox" tap point.  This seems to be a better place to tap the discriminator
then other published places.  I added a .1uf mono capacitor and a 1k
resister in series between the tap point and the mini plug.  It works great
for me, I get a 99% decode rate in Trunker.
Here is the link for the discriminator tap, it includes a picture are makes
it very easy to find the tap point:

http://www.geocities.com/Area51/Hollow/4346/2003_bc895_tap.html

Good luck!
Mike Curtis