The AT-910 is a TCAS Directional Antenna used in the TCAS 3000 system. The TCAS 3000 system provides pilots with bearing determination accuracy (2° rms vs. 9° TSO specification) and extended range surveillance (up to 80 nm active, 100+ nm passive). Enhanced Air Traffic Control Radar Beacon System (ATCRBS) range, altitude and bearing-tracker algorithms reduce false tracks to less than 0.5%.  The AT-910 is a four-element, vertically polarized, monopole array that is capable of transmitting in four selectable directions at 1030 mHz. The AT-910 is then capable of receiving replies from all directions simultaneously with bearing information at 1090 mHz by using Amplitude-Ratio Monopulse techniques. The AT-910 has variations that come without a mounting plate or with a mounting plate that has either 4 mounting holes or 8 mounting holes.  The AT-910 mounting plates also vary between a 1.560 in. connector extension or a .705 in. connector extension. The AT-910 has either a flat base or a curved base.