气压保持

根据机车车型的不同，有两种控制制动管压力的方法：自动保持和较旧的手动保持。

在自动保持系统上，制动管压力会自动调节。司机可以直接将列车制动手柄设置到任何位置。向“应用”方向设置得越近，制动力越强，反之亦然。该阀门会根据手柄的位置自动处理制动管的排压或加压。

On non-self-lapping systems, the process is more hands-on. The lever has a few fixed positions. Two of the positions, called “release” and “service” can be thought of as adding and releasing the brake pipe pressure, respectively. The position in between them, called “lap”, is used to maintain whatever pressure is in the brake pipe. The furthest position, called “emergency”, will release pressure at the fastest possible rate.

Auxiliary reservoirs are being drained when braking. When the brakes are released, it takes some time for auxiliary reservoirs to fill up again. The lap position, however, functions only if the auxiliary reservoirs are full. To stay in full control over braking it is recommended to not release non-self-lapping brakes when knowing that moments later braking may be needed again. Calculated, slow moves are preferable when releasing the non-self-lapping brakes.

With both brake types, the driver can see exactly how much braking force they are applying by looking at the brake pipe and brake cylinder gauge needles.

两种系统都相当易于使用，尽管自动研磨对初学者来说可能更直观。简单来说，对于自研，控制装置设置所需的制动力，将其留给自动阀来完成工作，而对于非自研，控制装置直接设置制动力。

In case a train contains motorized vehicles with both self-lapping and non-self-lapping brake valve types, only the self-lapping ones will be functional when operating the brake. For that purpose, vehicles are also equipped with brake cutout valves, which can be used to isolate certain vehicles from the brake system and resolve this conflict.