This thing works great for the sonic combat modules. I've got them in 4 of my planes. The CTR is what you connect an open RX port to control the firing of the XPORT. The IN and OUT is only used if you want to enable the motor kill option. The ESC's THR servo goes to the IN and a servo extension wire goes from the OUT to the RX - for motor kill. All in all pretty cool and reliable unit.