A heat-assisted magnetic recording head includes a slider, an edge-emitting laser diode fixed to the slider, and an external mirror fixed to the laser diode. The concentrator converts ambient air into concentrated oxygen gas for the user and includes a plurality of adsorption beds and a rotary valve assembly. A different security code is generated for each account transaction for verification. The method further includes initializing the communication link between the first computer and the second computer in response to the acknowledgement message. The TFT substrate is formed with a notch at its portion connected with the flexible wiring substrate. The different ranges are automatically selected for different motor load conditions.