An instability detecting device, used for easily and simply detecting a rotating stall andor a surge frequently occurring during an operation of a turbo compressor, is disclosed. Embodiments comprise a method of transmitting information from RFID tags, receiving the information in an RFID tag reader, analyzing the information to select a number of employees to work in a work area, and dispatching one or more employees to or from the work area according to the selected number of employees. Also during calibration, the second flow control element is calibrated to the first flow control element. A gate circuit generates a gated strobe signal using the delayed enable signal that masks transitions of the internal strobe signal that occur prior to a valid region of the internal strobe signal. If a user instructs by filling in a physical medium on which the obtained page data is printed, an action identification code to be used for deciding an action corresponding to the instruction is prepared based on the page data obtained from the web server. In one embodiment, an RF-safe initiator, wiring, a detonating cord and a plurality of shaped charges are installed into the loading tube at a first location.