A text communication, such as an email or blog posting from a user, is monitored to identify an issue. Detection is independent of the application environment. The ball-releasing apparatus first comprises a tubular body. A photodetector detects modulated light obtained by modulating the light from the light source with the ultrasonic wave in the local region. Herein, an output part of initial gamma reference voltages selected in common as the first and second gamma reference voltages is shared with input parts of the first and second gamma reference voltages.