The correct answer is C) transducer. In modern fathometers, the sonic or ultrasonic sound waves used to measure water depth are produced electrically by a transducer. A transducer is a device that converts one form of energy (in this case, electrical energy) into another form of energy (sound waves). The transducer in a fathometer converts the electrical signals into the sound waves that are then transmitted into the water and reflected back to the device to measure the depth. The other options are incorrect because: A) A transmitter is a device that sends out a signal, but it does not necessarily convert the energy form. B) An amplifier is a device that increases the strength of a signal, but it does not generate the sound waves. D) A transceiver is a device that can both transmit and receive signals, but it does not necessarily generate the sound waves.