The invention relates to a system and a method for identifying encounters of the users of a system, wherein the user group comprises active and passive members. A butterfly valve is disposed in the intake channel of the carburetor and has a pivot range into which at least one fuel nozzle opens. In addition, the method includes the step of comparing a secondary sequence identifier from the secondary device with the sequence identifier in the primary device to detect a lost message. A fourth calculates an imaginary lane boundary line, wherein the imaginary lane boundary line is tangent to the lane boundary line at a point close to the predicted position. The apparatus comprises an optical stimulator configured to optically stimulate a nerve area affecting a person’s balance, and a control module coupled to the optical stimulator, the control module being configured to control the optical stimulator. A silicon oxide film is formed on a side surface of the gate electrode.