Furuno CH-300 - Manual (Page 76)

3. VERTICAL SCAN MODE
3-18
SECTOR control
For the vertical scan display: When the display sector is 6° (minimum) the tilt angle of the
horizontal and vertical scan modes are interlocked and each transmission on the horizontal
display is reflected on the vertical scan display. The message TILT ANGLE MONITOR
WINDOW momentarily appears on the screen and the vertical bearing cursor disappears.
Note:
Only the SECTOR control may be operated in this condition.