Furuno SC-120 Operator's Manual page 27

The reference direction is as shown below. The mounting method is the same as
that for mounting on the deck.
Reference Direction
Mount processor unit so
reference direction is
within ± 2.5 of
fore-and-aft line.
POWER switch
(power lamp)
Bow
Mounting Method: Invert
Mounting Direction: A
Starboard
Port
DIRECTION "A"
Stern
Bow
Mounting Method: Invert
Mounting Direction: C
Port Starboard
DIRECTION "C"
Stern
Processor unit orientation, installation on the underside of a desk
Mount the processor unit on a level surface with its name plate facing the bow,
stern, port or starboard.
Connectors
Processor Unit, rear view
Port
Port
Name plate (other side)
Bow
Mounting Method: Invert
Mounting Direction: B
Starboard
DIRECTION "B"
Stern
Bow
Mounting Method: Invert
Mounting Direction: D
Starboard
DIRECTION "D"
Stern
2. INSTALLATION
2-13