A liquid dispenser includes a liquid supply channel, a liquid return channel, and a liquid dispensing channel. In particular, removable or repositionable ventricular partitioning devices are described. The detector array is configured to enhance spatial resolution and maintain high system sensitivity. Thus, it is possible to curb increase in a stroke and reaction of a brake operating member which would be invalidated by a brake stroke simulator when a hydraulic power source fails, and avoid insufficient strokes of the brake operating member even if spikes are inputted.