Gosh man years ago a lot of the cheaper units you just as well leave it on...the return without the symbol did not mean much more than the symbol. If you really worked at it you could get a little better at determining exactly what you were seeing without the symbol...but by the same token if you are observant and have a little bit of deductive skills you can figure out what your looking at a lot of the time. You have to know turbulence from the motor or trolling motor,turbulent water itself with a lot of suspended matter,etc can all throw a false signal. Knowing your waters and where fish are typically going to be and lots of experience goes a long way. Plus I am not going to fish for hours on end without a bite if I think the return may be a little suspect or I am not pretty confident of what species I am probably looking at. When they first came out had a pretty good mental map of a lot of the waters I fished already from having just fished them.But it made a HUGE difference when I could pull up to some standing timber and see which one of say twenty trees had fish among the limbs,and when I would follow along a creek channel and see fish and how they related to the channel rather than just fishing blind based on experience.On the big rivers catfishing if I was drift fishing and wasn't showing much and then all of a sudden drifted into an area showing fish all in about the same width of depth and over an irregular bottom and maybe some baitfish I knew the rods were fixing to bend. I use to call it sometimes when other people were fishing in the boat.If the fish were biting good and it was just a matter of getting it in front of them you could call the hits with a pretty high percentage. I could look at four different brush piles and tell you which one was the best prospect based on fish symbol returns.