The present invention relates to a method for monitoring a control channel and an apparatus thereof. A first signal is generated by a side impact sensor system. This is important when a plurality of slots having different functions contains identical circuit boards or modules. At least one supporting element is provided for transferring a pressing force that is applied in the direction of the base plate from the housing lid to the housing shell. The second fastening part has an attachment member attached to the base part and a fastening member fastening the second umbilical member to the attachment member, and the attachment member is provided detachably from the base part together with the second umbilical member in a state where the first umbilical member is fastened by the first fastening part. An ammonia ratio is usually set to a reference ammonia ratio which is determined in advance in accordance with an operating state of an engine.