A spectrometer measures a spectrum of a light beam supplied from a light source so as to obtain fine information and coarse information of the spectrum easily. The volume defines the three-dimensional imaging section, which is a three-dimensional section of a structure of interest. The float valve controls a second conduit which connects with a second container. A collarbeing rotatable relative to the fixed and movable sheaves is mounted between the drive shaft and drive pulley, and a one-way clutch mounted between the collar and the drive shaft interlocks the collar and the drive shaft so that only the rotation of the collar in the normal rotating direction is transmitted to the drive shaft. When the processor determines that the first sensed image is a fingerprint image, the processor further controls the fingerprint recognition apparatus to enter an operation mode. An apparatus for saving power on an xDSL includes a data rate statistics unit, a line rate adjustment policy unit, a line parameter adjusting unit, and a line rate updating unit for an xDSL transceiver.