🔍 Key Concepts

• Sound-powered telephone circuits and how they work without external power • Typical operation of a handset switch (press-to-talk or press-to-listen) • How voice energy is converted and transmitted in a closed circuit

💭 Think About

• Think about whether the circuit needs to be opened or closed for your voice to be transmitted over the line. • Consider what would happen if everyone on a circuit could talk without pressing any button—would that be practical on a noisy ship? • Ask yourself whether listening normally requires you to activate anything, or if it is usually passive once the circuit is live.

✅ Before You Answer

• Verify which function (speaking or listening) normally requires activating a switch in shipboard communication systems. • Consider whether the button’s main role is to close the talking circuit or to activate some other feature like ringing. • Be sure you are choosing between: button needed for both actions, only for speaking, only for listening, or for calling another station (ringing).