Need help about initial Hardware

hello all.
i am new to asterisk just started work .
i am at very initial stage…
i have a small project to make campus to campus communication .
i want to know how many hardware card for my PC do i need for server?
basic idea of my project is in Picture that is attached with this post.

after this if i like to add 1 PSTN line in any server then what card i should add…? please help

You don’t need any extra hardware for campus to campus communications.

You only need a card when you add the connection to PSTN. I don’t use that part of asterisk, so I can’t tell you what hardware to get for that.