If you Google Austrak Tractor one of the results points you to a new AUSTRAK Tractor forum.

This forum   has been set up by a chap who has a long history of working on and with Austraks.  I would recommend that anyone here seriously interested in the RT45 should keep an eye on that site as well as this one. Norris who goes by the nick name Turtle has a wealth of knowledge that he is more than willing to share.