I didn't know this till last week as well. I was having some crosstalk interference from my 2 Birds mounted on the console, both transducers are mounted on the transom. I set the filter up on medium on both units and all the interference I was having was gone! I think I'll try the low setting next time out and see what happens. I had tried adjusting the frequencies on both units with very limited results for the last couple of months, this really solved my issue.