How does transmitter works in echo sounder?

The echo sounder is essentially a speaker (transmitter) and microphone (receiver) in one single unit. The speaker sends out a pulse of sound, and the time taken (in seconds) for the pulse to return to the microphone is multiplied by 1.5. This gives the distance (in kilometres) to the object the echo sounder was 'aimed' at. The most common use is as a depth sounder for ships.