Travis Jordan wrote:
I don't know of any reliable 'low price' 4 km remote phones. Here is
one higher-priced option; obviously, it would be illegal to use one of
these in India without a proper license (which may not be possible to
obtain). You may also want to mount gain antennas at both the remote
and local end to insure reliable service.

http://www.nordsudtt.com/voyager/

Here is what looks like the same phone at a more reasonable price:

http://www.thehightechstore.com/voyager2200.html