BENDIXKing AeroNav 910 Pilot's Manual page 223

AeroNav 900/880 Series Pilot's Guide
Some radar systems (e.g. RDR 2000) can be configured at
installation to include the Target Alert feature. The purpose of the
feature is to alert the pilot to the presence of a significant weather cell
that exists beyond the currently selected range. For this mode to be
active, "On" mode must be selected and Vertical Profile must not be
selected. The criteria for a Target Alert is for the cell to be at least red
intensity, within ±10° of aircraft heading, a minimum size of 2 NM in
range and 2 degrees in azimuth, and within the range of 80 to 240
NM. When a Target Alert is issued, two red arcs, separated by a
black arc will be displayed at the top of the display centered on the
aircraft heading (see the following figure). Target Alert is applied to
each scan independent of the other when the radar is alternating
scans.
Target Alert Depiction on Radar Tab
89000039-010
Rev 1 May 2019 Map Subsystem 4-73