Junction box , FJB101 , is used when there is a large distance between the mounted ball valve and relay receiver. For example, the ball valve mounted in one building and relay receiver and remote control in another building . Another option is that the ball valve is in an inaccessible basement with thick concrete walls that attenuates the signal from the wireless keyfobe. A third option is that you want a signal light that illuminates when the ball valve is open.
There are two outputs in addition to the ball valve output which can be switched to the Pressure drop transmitter FPT101 on one of the outputs.