Working principle:the ultrasonic transducer is used to transmit the signal, which is transmitted through air or water, and the signal is fed back by the ultrasonic contact with the object in the water, and then processed by the internal processor, and then displayed on the screen. If you are looking for a gift for your husband, father, friends or any anglers, then look no further, the fish finder is now ever. Simulated demonstration mode, convenient for users to understand how to use LCD display Depth detection range:100m, degree:10cm User can customize the measurement unit:meters or feet Light green screen backlight Battery saving mode High/low sensitivity setting Fish position depth scale Probe:can be floating on the water or installed on the ship's side 200KHz sonar frequency 45 degree probe detection angle Power Suplly:4 batteries for power supply(but not included in the item) IPX4 waterproof design Unit weight:0.578kg Colour:Yellow Material:PVC Package Contents: 1 set * wired fish detector Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.