Hi Mickwah and
to the forum,
The brake switch is used to automatically disable the power going to the motor and engage the regenerative braking
(EBS) when the brakes are applied.
With the internal Vector controllers on the GM hubmotors the function is either On or Off rather than being variable, so I'm guessing that it will probably be the same
(just On or Off) on the larger external Vector controllers too.
If your vehicle already has a 12V brake light system you can simply use the 12V connection from the brake light to control the regen/EBS via the +12V high brake wire.
Alternatively, the +5V and GND connections are simply switched together to activate the regen/EBS through a separate brake switch.
The brake switch also disengages the cruise control if it is active when the brakes are applied.
Alan