"How long does it take you to change the figures? Can't be more than 20 secs, and if a mid-air were to happen in that time, the separation up to that point must have been noticed"
You may be doing a fine job seperating me from your traffic, but the TCAS is showing me the traffic you may not be seperating me from. In the LA area the vast majority of TA/RA's are on VFR traffic that I'm not being seperated from. The controllers there do an absolutely superb job of keeping me away from IFR traffic that they may not have time to point out a VFR aircraft to me, the TCAS aids in that. Hitting a VFR aircraft hurt just as much as hitting an IFR one. That said, never turn off the txponder.