PurposeUSED TO PROVIDE ELECTRICAL ACCESS TO WATER TANK QUANTITY TRANSMITTER FOR CALIBRATION. THE TEST BOX IS USED TO PROVIDE ELECTRICAL ACCESS TO THE 6251-1 WQMS CONTROL MODULE VIA THE CALIBRATION AND DEBUG PORT ON AIRPLANE MODEL 747-8 AND 777.Airplane747, 777-200, 777-200ER, 777-200LR, 777-300, 777-300ER, 777-8, 777-9Usage CodeMAINTENANCE 