Simrad Robertson AP9 Mk3, Instruction Manual, Page: 63 / 202

Design and theory of operation
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3-5
2. By the PORT and STBD one-degree-course change-buttons, also
when operating in the AUTOPILOT mode
3. By navigation receiver in CTS or Mixed Nav. steering modes.
During operation of the autopilot, only one compass (main compass
or steering compass) will provide ship's heading reference for auto
steering. The other compass (monitor compass) is only used to
compare the main compass heading and eventually trigger a
COMPASS DIFFERENCE alarm. The setting of the limit is made by
altering the OFF-COURSE LIMIT value.
P S
COURSE
SELECT
NAV. OFFSET
COURSE
TO STEER
NAV. REG.
NAV.
REC.
NAV. COURSE
XTE
CTS
COURSE TO STEER
STEERING COMPASS
MONITOR
COMPASS
SHIP'S
COURSE
HEADING REF.
AUX. COURSE
DISPLAY
COURSE
COURSE
ERROR
OFF COURSE
ALARM
COMPASS
DIFFERENCE
TO PID
REGULATOR
MAN
AUTO
NAV
AUTO
NAV
COMP. SELECT
COMP. SELECT
COURSE SELECTOR
NAV.
REC.
Fig. 3-5
AP9 MK3 Course Handling
This means that even with one compass connected, the OFF-COURSE
warning will still be active, but NO COMPASS DIFFERENCE will
occur.
The COURSE ERROR signal for the PID regulator is determined by
the steering compass heading and the course selector/one-degree
buttons.
When switching for NAV mode, the course selector and one-degree
buttons are disconnected. The heading will then be determined by
the NAV OFFSET signal from the XTE navigational receiver or from
the CTS SAT.NAV receiver.
Selection is made by the INFO LOOP 2, Nav. Steering Type
XTE/CTS/ PRIORITY.