A sonar transducer is a combo speaker/microphone. It broadcasts SOUND that the display produces and detects the return echoes that the display calculates. It doesn't do anything on its own and has no power source. Without turning the unit OFF, you can just turn SONAR OFF and the unit will be a Chart Plotter. If your unit is new enough it has a STANDY setting that also turns off the sonar pulses==no start-up time to get going again, just push the power button.