The present invention is directed to a coupler for providing fluid connection between a needle holder and an intravenous needle assembly. The devices are connected in series through an insulating film using a wiring layer formed on the surface of the substrate. In plan view, the inner face of each of the side branches of the shoe also comprise a zone which has a simple curved inner profile and which is narrowed such as to be narrower than zone C of the front central part or toe piece. On receipt of the command at the first storage system, the data is written to the first logical volume. The clock signal is then restarted to operate the SPI slave after the first buffer is refreshed. In the plurality of holding circuits, a value of the control signals held by these holding circuits is changed by external devices according to a probabilistic search technique so that the digital system operates correctly in relation to operation timing.