Our military friends generally have their transponders on so their own people can see them! It also helps us see them as well. Only when they are going to do naughty things to other people do they turn them "off" (or park them in a sneaky way so that only their own side can see them). ACAS/TCAS is an SSR application. Big Fraidy Cat - I'd suggest that you try and ignore any press article which has the words: alarmed, violent, storm, frightened, collision, narrowly missed, emergency, stalled, tailspin, etc... In fact any any article with any emotive or sensational terms.
Unless the threat traffic very rapid vertical closure rate, the information and warnings you receive are generally as follows: Visual (shown on a sort of map display): Hollow blue diamond, other traffic, Solid diamond, nearby (proximate traffic), Solid Amber circle: Threat traffic and Solid red square for traffic which you being instructed to avoid. The aural warnings only start with "Traffic! - Traffic!" when the traffic is first shown as a treat. When the system starts to instruct you take avoiding action, the intruder is shown as a red square. There is a simple write up on
http://www.aerowinx.de/html/tcas.html.
And finally, ACAS stands for Aircraft Collision Avoidance System and TCAS, which is the same thing, is Traffic Alert and Collision Avoidance System.