A method of data recording and reading for a memory device employing magnetic domain wall movement. The controller includes a lighting source in which electric discharge is caused between opposed electrodes to radiate light, a reflecting mirror for reflecting a flux of light radiated from the light source to control the light flux angle, and travel path changing mirror for changing the travel path of the flux of light whose divergence is controlled by the reflecting mirror. By adjusting the gain of the variable gain amplifier, the received signals can be amplified or attenuated in accordance with design requirement. Other embodiments provide methods and apparatus for determining an anticoagulant therapy factor without requiring use of a mean normal prothrombin time determination or ISI. A spacer received in the second passage of the housing is engageable with the fastener and the longitudinal member.