Ground Service Bus vs Ground Handling Bus B777

[Rook]

Hello,
Can anyone tell me the difference between the Ground Service Bus and the Ground handling Bus on the B777 and how they are related? The manual says:
"Ground Service Bus
The ground service bus is normally powered by the right main bus. Alternate sources of power for the ground service bus are:
• the APU generator
• primary external power.
The ground service bus powers:
• the main battery charger
• the APU battery charger
• miscellaneous cabin and system loads.
Note:
some A/C have a Ground Service switch incorporated in the cabin:
• At door 1L

Ground Handling Bus
The ground handling bus can be powered on the ground only from the APU generator or from the primary external power source. It is provided for loads such as cargo handling, fuelling/defuelling operations, and other equipment energized only during ground operations."

But the schematic only shows the Ground services bus not the ground handling bus. Also, would the CABIN/UTILITY button in the flightdeck control both or just the ground services bus?
Any help is appreciated.

[vapilot2004]

Generally the ground handling bus (AC & DC) powers loads that are only used on the ground such as the fueling panel, interphones, cargo doors and lights. This bus is not powered in flight or during takeoff, taxi, or landing.

Ground service buses power loads such as cabin equipment and lighting and the battery chargers/TRUs. This bus will be powered automatically when one of the main AC buses are powered (usually right main) or can be switched when external or APU power is available.

[Rook]

excellent. Thanks very much.

[NSEU]

Generally speaking, the Ground Handling Bus (GHB), Ground Service Bus (GSB) and main busses (in that order) provide power to progressively more and more aircraft systems.

The GHB provides power to certain systems useful to personnel outside the aircraft working with cargo loading, etc. GHB power requires no buttons to be pushed. GHB power is automatically applied to the aircraft when the external power leads are plugged into the aircraft (and the power unit is turned on, of course). GHB power may also illuminate specific lights inside the aircraft to allow you to find your way to the flight deck.

The GSB provides lots of useful power for cleaning staff inside the aircraft and, as previously mentioned, power for recharging batteries. Normally there is a switch somewhere in the cabin to turn on the GSB. The GSB can also use this external power source. However, I guess the expression Ground Service Bus is a little misleading, as it can be powered in flight by main busses, whereas the GHB can't.