Provided is a band gap constant-voltage circuit which is configured by combining a PMOS transistor, an NMOS transistor, a bipolar transistor, and a resistor, and is capable of preventing an output voltage from being stabilized at 0 V immediately after power supply fluctuation. And there is provided a method for transmitting an optical signal through a fiber comprising: producing a frequency modulated signal; passing the frequency modulated signal through a multi-ring resonator optical spectrum reshaper so as to convert the frequency modulated signal into a substantially amplitude modulated signal; and passing the substantially amplitude modulated signal into the fiber. The machine-related data is updated based on the data received from the multiple exercise machines and one or more operations is automatically performed with reference to the stored machine-related data to produce operation-generated information about one or more of the multiple exercise machines.