
APRA-SPECIFIED FACILITIES
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detected, the 'target lost' warning is activated and the
last observed position of the echo is marked on the
screen. It is also normal to activate an audible alarm.
4.7.4 Performance tests and warnings
The ARPA should provide suitable warnings of
ARPA malfunction to enable the observer to monitor
the proper operation of the system. Additionally, test
programmes should be available so that the overall
performance of the ARPA can be assessed periodi-
cally against a known solution.
In the case of conventional radar, there was always a
basic requirement to ensure that the radar controls were
properly adjusted and tha ...