Panasonic KX-HTS824 Getting Started page 46

3.2.5 Installing/Removing the Optional Service Cards
Installing an Optional Service Card in the Free Slots
In the Main Unit, there are free slots for trunk/doorphone cards and free slots for extension cards.
In the free slots for trunk/doorphone cards, you can install one each of the following cards: LCOT4, DPH2.
In the free slots for extension cards, you can install one or more of the following card: SLC8.
For details, refer to the description of each optional service card in "3.3.2 LCOT4 Card (KX-HT82480)",
"3.3.3 SLC8 Card (KX-HT82470)" and "3.3.4 DPH2 Card (KX-HT82460)".
A Trunk/Doorphone Card Slots
B Extension Card Slots
1.
Remove the dummy cover plate for the Free slot.
Cut off any excess plastic in order to make the surface smooth.
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A
B
B