If I connect my transmitter to receiver .
The RX voltage bar notifying low battery on transmitter screen.
I'm using flysky i6 transmitter and I6B receiver.
Is there any connection with FailSafe Setting ? or What is solution for this issue ?

Aux channels can be used to activate different flight modes, and control different peripherals on a quadcopter such as a lost model buzzer and LED light. With new technology being updated all the time the amount of functions and peripherals we can control from the transmitter are increasing every day.

I don't understand what Jesse00 is saying, but try a different battery and see if there is a difference. Have you checked the Rx battery? This could be a signal problem too, or a radio malfunction. Eliminate the possible causes one by one