can anyone tell me about Dual backup and dual receiver system onboard?
ravi

It is a failsafe, redundant mechanism of connecting two receivers (Same type to completely different bands) and two power sources to the array of Servos in your plane.

http://www.powerbox-systems.com/e/powerbox_systeme/powerbox_royal/start.php
http://www.powerbox-systems.com/e/powerbox_systeme/powerbox_royal/start.php

The plane will continue to fly even if one of the batteries dies And one of the receiver does not get proper signal. People usually use it in large scale planes where the cost of losing the  plane is much, much more (USD 2k+) than putting such ridiculously priced box (USD 350).