The present invention provides a technique for continuous measurement of blood pressure based on pulse transit time and which does not require any external calibration. The RFID system includes an RFID repeater receiver located outside of the operable range of a target RFID tag; and, at least one RFID repeater positionable within an operable range of the target RFID tag. This eliminates the need of a conventional construction where a spring or others are used to drive a flexible membrane of the discharge pump to the operation chamber side to take in the resist liquid. The service is executed according to the first information, and then the second information is analyzed. A 4:3 aspect ratio monitor displays the main video as is.