Mitel 300 Installation And Maintenance Manual page 19

To Locate the PSTN Module in the Expansion Module:
Remove the Expansion Module by firstly opening the Expansion MDF cover
Open the Expansion Module and remove it from the MDF
Insert the PSTN Module (or modules) on the MDF connectors
The upper slot is the first module position
Mitel 3000 Australia Installation and Maintenance Manual
18
First network
module