A mobile radio communication system which sets a radio circuit efficiently without deteriorating the communication quality even when congestion of communication channels occurs. The rotary machines have one or more stages and each stage has one or more rotary components. The instrument can be used for off-axis cavity ringdown spectroscopy, off-axis integrated cavity output spectroscopy, or other cavity-based spectroscopy applications. Within the LED driver, the level of the LED current is determined from a boost voltage that is substantially a regulated dc voltage generated from the rectified ac signal. The gate driver circuit receives the PWM signal and converts the PWM signal to a first driving signal and a second driving signal.