A hanging sign is provided for displaying messages. Requests for services are inspected at an application layer of a network. The carriage remains in direct and continuous contact with the linear actuator and the guide at the first notch and second notch, respectively, when the carriage moves linearly back and forth along a travel axis. The first long edge of the shield wraps under the debossing of the first long edge of the base plate. By supplying and withdrawing pressure fluid to and from the bags, the roof may be moved between extended and contracted positions. At least a portion of the upper electrode and that of the lower electrode oppose each other through the piezoelectric film, and at least a portion of the periphery of the upper electrode is reversely tapered.