ComNav P4 Installation and Operation System Overview
Document PN 29010100 V1r0 - 30 -
Signal Processor Unit
PN 20140002
As seen in Figure 5, the Signal Processor Unit (SPU) accepts a number of inputs from the
other components of the autopilot system, and then processes them as necessary to control
the movement of the vessel’s rudder to maintain a given heading. As well as steering the
vessel, the sophisticated software within the SPU continually checks all aspects of the
autopilot’s performance, and will advise the user via the Control Head if any problems are
encountered.
The SPU is the central hub for all the wiring for ComNav analog or NMEA0183 devices in the
system, with 12 connectors for all power and input/output signals (such as DC power,
ComNav Rudder Feedback, ComNav RAI, NMEA 0183 Interfaces and Rudder Drives and
Interfaces). The P4 SPU connects to a NMEA 2000 network or standalone with a supplied T-
connector to the P4 Head, via a supplied 1m NMEA 2000 (Pigtail & Male End) cable at the
Network Port of the SPU.
It also contains a diagnostic section, containing several status and activity LEDs, some test-
points for service use, adjustment controls, and the system’s two fuses. The diagnostic
section has a metal cover with screws, which can be easily removed to view the LEDs and
the status of the fuses.
Figure 5 – The P4 Signal Processor Unit (SPU) showing wiring details
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