[Haskell-beginners] Understanding syntax problems

[Nathan Huesken]

Hi,

Reading this:
http://netsuperbrain.com/blog/posts/introducing-reactive-events/

I stumble upon this:

type BellMachine = Event () -> Event ()

Google did not tell me, what this means.
I understand

type BellMachine = Event()

but the rest is completely strange to me.

What does it mean or where can I find out?

Thanks!
Nathan