A receiver receives signals and noise over a frequency spectrum of a desired received signal. The desired received signal is spread using code division multiple access. The received signals and noise are demodulated to produce a demodulated signal. The demodulated signal is despread using a code uncorrelated with a code associated with the desired received signal. A power level of the despread demodulated signal is measured as an estimate of the noise level of the frequency spectrum.

A reading device connected to an external device include a transport section configured to transport a document, a reading section configured to read the document transported by the transport section, a data generation section configured to generate image data of the document read by the reading section; a transfer section configured to transfer the image data to the external device, a notification section configured to notify information to a user, and a control section, wherein the control section is configured to control a transport speed of the document by the transport section based on a transfer speed of the image data by the transfer section and, when the transport speed is changed, to cause the notification section to notify using a change notification A1 indicating a change in the transport speed.