In a diesel engine, heavy EGR lowers a combustion temperature, which greatly prolongs an ignition delay period and all fuel is injected within the ignition delay period, thereby performing a low-temperature premixed combustion. In order to improve the anchorage of the child seat in the upper region, the holder has a spacer device. A pivot arm is pivotally mounted adjacent a rear end of the housing for pivotal movement between a latching orientation in which the transceiver is fully nestingly engaged in the housing and a delatching orientation in which a force pivots the arm against the transceiver to move the transceiver out of the engaged orientation. For example, moving certain optical components within the optical system may cause the change in cutoff frequency.