Furuno BB FAR28x7 - Manual (Page 155)

3. ARP OPERATION
3-23
3.12.2 Acknowledging CPA/TCPA alarm
To acknowledge and silence the CPA/TCPA alarm, press the [ALARM ACK] key
on the keyboard, or choose the ALARM ACK box with the trackball and then
push the left button.
The warning label COLLISION and the flashing of the triangle plotting symbol
and vector remain on the screen until the dangerous situation is gone or you
intentionally terminate tracking of the target.
Note that when the COLLISION alarm is generated the AIS display is
automatically turned on.