Mitsubishi Electric 800 Series Instruction Manual page 14

 Insertion positions of screws and spacers (Ethernet model)
Mounting screw
Connector 3
Spacer
Connector 2
14
INSTALLATION AND WIRING
Spacer
Mounting screw
Spacer
The option connector 2 cannot be used because the Ethernet board
is installed in the initial status. The Ethernet board must be removed
Connector 1
to install a plug-in option to the option connector 2.
(However, Ethernet communication is disabled in that case.)
Mounting screw
Spacer