On behalf of Megatron, I'm posting the a pic of the TCAS II used in the B747-400 aircraft. Unlike the TCAS I. the TCAS II provides pitch commands to the pilot.
Traffic Advisory (TA): TAs are given to the pilot in form of the word TRAFFIC displayed in yellow on the ND, and the aural voice annunciation "traffic, traffic". This is not the highest alert level. Its purpose is first to call attention to a possible conflict.
TCAS triggers a TA as soon as an intruder enters the TA specific DMOD or tau area. If bearing information is available, the intruder can be identified on the ND by a yellow, solid circle. Otherwise, the circle is removed and lateral distance and relative altitude with vertical motion arrow (if motion is detected) is displayed in yellow numbers under the word TRAFFIC.
Resolution Advisory (RA): The highest alert level. Its purpose is to resolve a conflict by providing the pilot with aural and visual pitch commands. The pilot has to disengage the autopilot immediately as the escape maneouver has to be flown manually. Flight director commands as well as ATC advisories have to be ignored. The pitch command of an RA has always the highest priority.
TCAS triggers an RA when a target enters the RA specific DMOD or tau area. If no altitude data is available from the target, an RA will not occur.
If bearing information is available, the intruder can be identified on the ND by a red, solid square. Otherwise, the square is removed and lateral distance and relative altitude with vertical motion arrow (if motion is detected) is displayed in red numbers under the word TRAFFIC.
Other Traffic: ItÂ’s a TCAS term for targets detected within a range of 40 to 7 NM from the own aircraft and -- if the target sends altitude information -- within 2700 and 1201 feet relative altitude. These targets are represented on the ND as outlined white diamonds. They do not represent an alarm.
Proximate Traffic: ItÂ’s a TCAS term for targets detected within a range of 6 NM from the own aircraft and -- if the target sends altitude information -- within 1200 feet relative altitude. These targets are represented on the ND as solid white diamonds. They do not represent an alarm.
More info here
http://www.aerowinx.de/html/tcas.html