The brake interlock electrical system performs two functions.
The interlock system prevents the operator from propelling the
machine when the parking brake is applied. The brake
interlock also prevents the parking brake from releasing when
the propel control lever is not in the neutral position.
The brake interlock electrical system is composed of the
following main components: fuse (3), neutral start switch (4),
relay "P9" (5), relay "P6" (7), relay "P7" (8), axle interlock valve
(9), and drum interlock valve (10).