A petroleum well has an electronic module and a number of sensors which communicate with the surface using the tubing string and casing as conductors. The toner has excellent toner properties including low temperature fixing properties, anti-blocking property and anti-offset property, etc. An apparatus for sending control signaling is disclosed. The magnetic field generator comprises an inner ring-shaped magnetic field generating portion and an outer ring-shaped magnetic field generating portion, both of which are provided outside the vacuum chamber in a concentric relationship with the vacuum chamber and are independently rotatable with each other. When the main-curing irradiation section emits the second electromagnetic wave, a dot forming surface of the medium faces the lower side in the direction of gravity. Two tops of the two buckling ears are matched with the restraining arms.