A fluid-operated actuator assembly has a valve with an inlet for connection to a pressurized fluid source, a bi-stable electromagnetic device for operating the valve, which has a first state closing the valve and a second state opening the valve, a hydraulic actuator, and an electronic control circuit. The characteristics of the brake system is that when the bicycle is stopped at high speed and an initial force is generated, when the initial force is larger than the spring forces in the brake system, the system generates a buffers the initial force so as to prevent the disk from being clamped overly. A battery operated motor and onoff switch are incorporated into the handle end. The p-side electrode having this five-layered structure realizes an ohmic contact and high reflectance at the same time. Based on the tree structure, a source can be generated.