I have read several manuals on the TCAS for the PMDG 737 series, but is this an active function in the 600/700 models? The switches in the radio stack are fully functional, but nothing appears on the main panel. Most of the reccomendations I've received have been to turn the TCAS to "internal" in the PMDG menu, but that isn't a part of my PMDG styles menu!
TCAS (well TCAS2 in fact) comes when you upgrade and get the -800/-900.
When you upgrade it replaces the Panel on the 600/700 as well as the new versions, and the new panel has TCAS2 on it.
It works really well - you'll be heading for the Traffic on purpose just to test it ! "WARNING TRAFFIC - INCREASE FLIGHT LEVEL"
Very clever stuff - just a tip if you get it - to switch it on you need to test the system while on the ground (this is true of real TCAS2)....
Open the Radio panel and rotate the TCAS dial to "TEST" - you'll hear "TCAS Test ok" ........ now turn the dial to TA/RA.
.... and you're off to look for planes.