If you invent one
then it exists in all times afterwards and would therefore be the receiver/sender

Some guy called Mallet was trying to make one with lasers or something. There was the outside chance that when he turned it on, he would get a 'message' from the future
( Citizen Cavy Admires your passion for conformity, Mon 12 Apr 2010, 16:08, 1 reply, 16 years ago)

This is making my head hurt now.
But you wouldn't be able to come back to a time when there were none, which is why no one has turned up from the future to show off their new time machine.

That's terrifying! I take it he didn't manage it?
(Applebite Uh! A cow!, Mon 12 Apr 2010, 16:14, Reply)

i don't know
the theory went that he could send individual atoms, not sure it's a finished project, yet
( Citizen Cavy Admires your passion for conformity, Mon 12 Apr 2010, 16:17, Reply)

this is why time travel on TV shows
makes me angry, it always raises more questions than it answers. Especially when the TV show is Futurama.
( Kitty v1.0 desperately naive, Mon 12 Apr 2010, 16:17, Reply)

well a lot of it depends on how you understand (or represent in fiction) time itself

( Citizen Cavy Admires your passion for conformity, Mon 12 Apr 2010, 16:18, Reply)