Furuno CSH-5 MARK-2 Operator's Manual page 63

Gray Test
The gray test checks for proper display of monochrome characters
and markers. Concentric rings and a monochrome test bar are dis-
played.
PRESS [MENU] 2 or 3 SECONDS TO STOP SELFCHECK
Echo-2 Test
The echo-2 test checks echo processing circuits in the transceiver
and display units.
PRESS [MENU] 2 or 3 SECONDS TO STOP SELFCHECK
Set the VP control on the main
panel to "OFF" position.
Radial pattern as above is
displayed.
57
GRAY TEST
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