🔍 Key Concepts

• How sound-powered telephones work without external electrical power • Which systems on a ship rely on the ship’s main or emergency electrical distribution (switchboards, batteries) • What it means for equipment to be independent of ship’s power in an emergency

💭 Think About

• If normal and emergency power both fail, which of these options could still let the phones operate? • Do sound-powered telephones usually depend on the ship’s electrical system, or do they create their own energy in some way? • Look at the names of each choice: which ones clearly depend on the ship’s electrical network, and which one suggests a self-contained source?

✅ Before You Answer

• Identify which answers are tied to shipboard electrical systems (main or emergency) • Recall that sound-powered phones are designed to work even during total power failure • Check which option implies local, manually generated power at each station rather than centralized power