Doc, no apologies needed. Commercial airplanes and some private airplanes have both a weather radar and TCAS (Traffic Collision Avoidance System). Typically, they don't have radar that shows other aircraft like ATC or the military fighters do.
The Traffic alert and Collision Avoidance System (or TCAS) is an aircraft collision avoidance system designed to reduce the danger of mid-air collisions between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped aircraft which may present a threat of mid-air collision (MAC). It is an implementation of the Airborne Collision Avoidance System mandated by International Civil Aviation Organization to be fitted to all aircraft over 5700 kg or authorised to carry more than 19 passengers.
Official definition from PANS-ATM (Nov 2007): ACAS / TCAS is an aircraft system based on secondary surveillance radar (SSR) transponder signals which operates independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft that are equipped with SSR transponders.
In modern glass cockpit aircraft, the TCAS display may be integrated in the Navigation Display (ND); in older glass cockpit aircraft and those with mechanical instrumentation, such an integrated TCAS display may replace the mechanical Instantaneous Vertical Speed Indicator (which indicates the rate with which the aircraft is descending or climbing).
http://en.wikipedia.org/wiki/Traffic_Collision_Avoidance_System
