Hello Kuwait340,
Your friend is right. Newer TCAS models can detect aircraft up to 100nm.
Generally speaking, the older models can detect up to 30-40nm. The "enhanced" ones can detect up to 80nm and the brand new ones can detect up to 100nm.
We have a very mixed fleet (from s/n 02XX up to 38XX), and sometimes you can see the difference - especially during the enroute phase.
Also, the older aircraft only display traffic on ND at ranges 10,20 and 40nm. If you're using at a greater range, a message will appear to reduce the ND range to check the traffic inbound.
Check FCOM1 1.34.80 p1 and 1.34.80 p8 for more details...
