Originally Posted by
Capt Kremin
I have attempted to verify if the capability was present but am yet to receive an answer
Mon Capitaine, I wasn't able to turn up much beyond some promotional material on the Panasonic IFE but someone smarter than me found Boeing Service Bulletin 777-24-0075 (Original Issue: August 21, 2003) ELECTRICAL POWER - General - Install the Passenger Compartment Electrical Power Isolation Switches (Complete). The reason for the SB is as follows;
The change described in this service bulletin will provide new switches on the flight deck than can remove power from the cabin systems if smoke or flames occur. Smoke and flames in the passenger cabin can cause injury to the passenger and damage the safety critical cabin equipments.
We have received numerous reports of smoke or flames in the passenger cabin related to the wiring for the passenger cabin in-flight entertainment system, cabin lighting and passenger seats. It is not easy to remove the electrical power to these systems to stop the smoke or flames. Two switches can be installed to remove power from some of the passenger cabin electrical systems.
When selected OFF, the IFE/PASS SEATS switch will remove power from all the components of the IFE (in-flight entertainment) system and the passenger seats (seat motor power, personal computer power outlets and telephones).
...
Among the IFE components that are to be depowered when the IFE/PASS SEATS switch is selected OFF are the Cabin Telecommunication Unit, the M1/M2 Galley Handsets and all the telephones, both seat and wall mounted.
Bearing in mind the timing, a couple of years after the final report on Swissair Flight 111 was handed down, you get the sense that this SB is meant to ensure,
inter alia, that the IFE/PASS SEATS switch removes power from
all IFE components including the phones. To that end the test procedure includes the following:
f. Do this test of the IFE/PASS SEATS switch.
(1) On the P5 panel, select the IFE/PASS SEATS switch to OFF.
(2) Make sure that all the IFE equipment in the purser work station or video control center
no longer has electrical power. Some components may have battery backup units. For
these components it may take several minutes before the electrical power is removed.
...
(7) For airplanes with wall mounted telephones, make sure that the telephone does not
operate. ...
I wouldn't necessarily call this slam-dunk definitive but it certainly strongly suggests that the IFE/PASS SEATS switch takes down all passenger cabin telecommunications.