🔍 Key Concepts

• Echo sounder transducer operation (what it does while transmitting vs. receiving) • Difference between electromagnetic energy and acoustical (sound) energy • Whether an echo sounder uses radio frequency (RF) or audio/ultrasonic frequency (AF) signals at the transducer

💭 Think About

• When the ship is sending out a ping, what form does the energy have inside the cables, and what form does it have in the water? • When the echo returns from the seabed, what must the transducer do to that sound so the electronics can process it? • Look at the oscillator feeding the transducer in the block diagram: is it labeled in kHz like sonar (audio/ultrasonic) or like typical RF radar frequencies?

✅ Before You Answer

• Confirm that the direction of conversion at the transducer is electrical → sound on transmit, and sound → electrical on receive • Check whether the diagram and labels around the transducer show AF/sonar frequency or RF stages • Eliminate any choice that has the transmit/receive roles reversed or the wrong type of frequency (RF vs AF) at the transducer