Power for the ground crew interphone system is supplied when which switch is activated?

• A. The battery switch is activated in either cockpit
• B. The aux battery switch is activated in the front cockpit
• C. The avionics switch is activated in the front cockpit
• D. The generator switch is activated in either cockpit

Answer: (A)

Power for the ground crew interphone comes from the aircraft’s main battery when the battery switch is ON in either cockpit. This energizes the main DC bus that the interphone relies on. The auxiliary battery switch Protects or powers only specific systems, not the interphone in normal operation. The avionics switch powers avionics equipment, not the interphone by itself. The generator switch controls generator output, but interphone power isn’t guaranteed unless the battery switch is also ON to energize the bus. So, activating the battery switch in either cockpit is what powers the ground crew interphone.