Fishfinder

A fish finder is an electronic device that uses >Ultrasonic waves transmitted by a Transducer to locate and display underwater objects on a monitor - with the target often being Fish or Fish schools.

Originally images were burnt on paper and in the early 1980's displayed on CRT screens and in the late 1980's on LCD screens.

Echo sounders determine the distance between its transducer and underwater objects such as Fish or seabed and show the results on the display.

An >Ultrasonic wave transmitted through water travels at a nearly constant speed of 4800 feet (1500 meters) per second. When a sound wave strikes an underwater object such as Fish or sea bottom, part of the sound is reflected back toward the source. The depth to the object can be determined by calculating the time difference between the transmission of a sound wave and the reception of the reflected sound. The sounder will then display this return as one of up to 16 different colors (color sounder) or a different level of gray scaling (monochrome sounder) depending on the strength of the returned signal.