A detection apparatus, a detection method and an electron beam irradiation apparatus for detecting deflection electrons in order to precisely focus even if a vacuum seal valve is provided. The method includes identifying features in each LDPC code having known error characteristics; adding each code to one or more categories based on the existence of such features; and ranking the LDPC codes according to the level of error risk. A recess portion is provided on one side of the raised portion to create a difference in the distances from an end surface of the connecting head to the raised portion and to the recess portion. The principle is also extended to mixed-rate signals, where for example some input channels are sampled at 48 kHz and some are sampled at 96 kHz . The power control circuit turns on the switching circuit for a specified period when power supply to the voltage controlled oscillation circuit is started. An electro-acoustic transducer attached to the bending wave panel excites bending waves in the panel to produce an acoustic output.