I bought this new and never opened it. The Raymarine guys told me I would need it with my electronics upgrade but I didn’t end up needing it as I converted all my sensors to digital. It is used to convert depth, speed, water temp, wind, rudder signals from analog sensors to digital and pushed that signal to your SestalkNG network. Unfortunate I can’t return it. I paid $239 plus shipping for it. $175 plus shipping.