A write-once high density optical recording medium capable of a high speed recording that effectively forms space between recording marks. The housing has a top, a bottom and an expansion slot defined in the top. Following the expiration of a predetermined time interval, which may be extendable, the stimulator switches back to the autocapture mode. Compression of the annular flexible seal forces the seal into sealing engagement with a cable extending along the throughway to provide a seal between the coupling body and cable. The stator core thereby becomes approximately equivalent to the armature in a direct current magnetism property, so that an electromagnetic actuator and a fuel injection valve that are excel in suction force and response are provided.