| Allow excess air pressure to be released from air tanks | |
| Deliver air from the air compressor to the air tanks | |
| Deliver air from the air tanks to the air brakes | |
| Allow water and oil to be expelled from air tanks |
| On every air tank connected to the air compressor | |
| On the last air tank connected to the air compressor | |
| On the first air tank connected to the air compressor | |
| On the air compressor |
| Parking and emergency brakes | |
| Duty, parking and emergency brakes | |
| Service, parking and emergency brakes | |
| Standard, parking and emergency brakes |