The power steering operates as follows.
Design and operation of Kamaz trailer brake drive devices
The brake drive of a trailer (semi-trailer) of a tractor vehicle is combined (single-wire and two-wire),
KAMAZ trailer brake control valve
The trailer brake control valve with a two-wire drive is designed to actuate the brake drive of a trailer (semi-trailer) when any of the separate drive circuits of the service brake system of the tractor are turned on, as well as when the spring energy accumulators of the drive of the spare and parking brake systems of the tractor are turned on.