At first glance, fishing seems simple: you need to find the fish and then catch them. For thousands of years, humans have been improving fishing gear, but the search and discovery of fishing spots were always done blindly, relying on the intuition and experience of fishermen.

After World War II, with the reduction of defense orders, fishing fleets began to acquire equipment based on sonar technology used for detecting submarines. At that time, echo sounders could only be used on large vessels because they were very bulky and required sonar antennas. In the late 1950s, the invention of transistors and piezoelectric ceramics for transmitters made it possible to create a compact and affordable fish finder. With advancements in computing and microelectronics, echo sounders were equipped with liquid crystal displays (both monochrome and color) and came with many useful features.

The name "echo sounder" aptly describes its operating principle: "echo" refers to the reflection of sound, and "sounder" indicates its function of measuring depth. This concept has been passed down through the ages. Combining the two gives you a device that uses sound reflections to measure depth.

An echo sounder consists of four main components:

• Transmitter, responsible for periodically generating high-frequency sound wave pulses.
• Receiver, used to capture and amplify signals.
• Transducer (also known as a sensor), which converts sound waves into electrical signals and vice versa.
• Display unit, which shows the detection results.

The transmitter releases sound wave pulses at regular intervals, which are transmitted into the water through the transducer. When the sound waves encounter fish, the seabed, rocks, or other underwater obstacles, they are reflected back. The returning sound waves are captured by the transducer and converted into electrical pulses. These pulses are amplified by the receiver and transformed into visible signals or sound alerts, which are then intuitively displayed as graphics or text on the screen for the fisherman to interpret and analyze.