Fuel Transfer MAIN 1 & 4 Switch

• ON - Opens the No. 1 and 4 Main Transfer valves to gravity feed tank 1 to tank 2 and tank 4 to tank 2.

Service Interphone Switch

• OFF - Allows independent operation of the Service and flight Interphone system.
• ON - Connects the Service and flight Interphone system.

OBS Audio System Switch

• NORM - Audio control in normal operation.
• CAPT or F/O - Connects the associated hand mic, boom mic/headset, headphone, oxygen mask mic, speaker and Control Wheel PTT to the Observer's Audio control panel.

Emergency Lights Switch

• OFF - Disarms Emergency Lights system.
• ARMED - Allows all Emergency Lights to come on automatically, if power to the No. 4 DC bus is lost.
• ON - Turns on Emergency lighting system. Lights are powered from their own batteries.

Fire/OVHT Test Switch
Introduces a Fire/Overheat signal to the engine, APU, wheel well, cargo and wing bleed duct leak detectors. The following occurs:

• Fire bell sounds.
• The following lights illuminate:
  • Master Warning
  • 1, 2, 3 and 4 Engine Fire Shutoff Handle
  • 1, 2, 3 and 4 FUEL CONTROL switch
  • APU Fire Shutoff Handle
  • FWD and AFT CARGO FIRE
• The following EICAS messages appear:
  • TEST IN PROGRESS displayed during test
  • FIRE TEST PASS or FIRE TEST FAIL displayed upon completion of test until test switch released.