North American 1200s were fitted with a 5-way combination splitter with pressure failure warning switch.
Warning Light Switch (brake line pressure differential)
There are two inputs (front and rear from master cylinder). And three output (two for each front brake, and one output back to the rear brakes. The electrical connector goes to the dash light.
It doesn't effect brake bias (it's not a Proportioning Valve).
Wiring
Brake_Wiring#Pressure_Loss_Switch