For ships constructed before May 25, 1980, weighing greater than 1,600 gross tons and for ships constructed after May 25, 1980, weighing greater than 500 gross tons. All vessels falling under this classification which sail international routes must be fitted with an echo sounding device. Electrically operated instrument that emits a sound from vessel’s submerged surface and then measures and records the time interval which passes before the echo returns. The most popular model is shown here. Please ask for further information and brochures of various models available from local manufacturers when required.