What Am I?

Be fair, attentive, and customers
will return.

Alexander Bain was the first to
design me, about a century ago. I'm
user friendly.

My photo sensor can focus on a small
piece of paper. The drum rotates,
helps me read what's on paper.

Do you know me?

Maybe, you don't.

Paper is sent through me.

When what I send reaches its
destination, there's another
rotating drum.

Any kind of information can
be sent through me.

I require a modem.

You know, now, what I am?

Answer:
I'm a fax machine.