Hi Phil, go to the link below, when you get there, do a search on TCAS and it will take you to their TCAS pages, and you will find everything you ever wanted to know about it. The latest systems, what they do and how they do it. There is a downloadable manual too which is a good read.
Hope it is of help.
Regards,
Woop woop traffic.........
http://lists.arinc.com/products/index.html