RE: Servo recoil
the site say it can work with out the battle unit pcb .
Use to simulate recoil of a cannon. Connect between a servo and the battle circuit. When the battle circuit fires a servo will recreate the action of a gun recoil. Contains a separate regulator for the servo.
This can also be used alone. There are three connections, power, ground and trigger. When the trigger wire is pulsed high the servo will activate.