The binding function stores the TX signal unique ID code and PPM frame rate and number of servos into the receiver; this must be done every time the number of servos is changed on the RC unit. (or another RC with PPM system)
The binding process is the same on Tx700Lite.
Instruction video on how to bind and store failsafe - http://www.youtube.com/channel/UCS2wXoorQHQaYmoSLE5_esg
If you use external battery for the LRS TX, then the binding procedure is a little bit different, leave the RC unit on ALL the time and connected to the LRS TX, the power on/off to the TX as mentioned in the binding procedure is only the LRS TX, now it will work, the binding mode is only activated when button is held down while power to the LRS TX is applied.