The present solution relates to a method in a first communication node for suppressing noise in a communication system utilizing an automatic gain control. During the giving of a presentation, multiple controls are available in the system which enable the presenter to have direct control of the presentation environment. The optical module includes at least a radiation guiding unit and at least an anti-glare unit. A WWUID search unit searches for the same WWUID in backup management information of a previous day stored in a backup destination. The hydrogen sensor has a high sensitivity and a low response time due to the relatively large membrane surface and the low housing volume. The substrate of the microfluidic device is preferably fabricated of a polymer such as polydimethylsiloxane.