Design question

What would I need if i’m NOT using VoIP.

The setup is 3-4 hardlines.
4-7 regular phones.

I can’t find an answer to these questions:
Do I need an FXO/FXS card for EACH of these lines? or some?

Also, if i have a regular phone, is it possible to have a voip adaptor, and use the internal network but still have the call leave via the hardline?

Do I need an FXO/FXS card for EACH of these lines? or some?

FXO connects to your telephone line or pots line
FXS connects to your telephone

Also, if i have a regular phone, is it possible to have a voip adaptor, and use the internal network but still have the call leave via the hardline

This is one of several different devices for that purpose

digium.com/index.php?menu=pr … duct=S101I