The fundamental substances of a neutron star black hole are neutrons, and there are no charges in a neutron star black hole. The supermassive black hole of a quasar has much greater universal gravitation, and electrons and protons must not exist. Because there are no charges in the black hole, the black hole has only a gravitational field, and it cannot generate electric and magnetic fields, and it cannot emit photons. Hence, a black hole is essentially a dark star. This paper reveals that a pulsar black hole has an accretion disk that rotates at a super-high speed. The positive ions in the high-speed rotating accretion disk, generate a super strong pulsed magnetic field at the two poles of the pulsar black hole. The high-speed positive ions and free electrons in the accretion disk decelerate violently in the process of random collisions and generate high-energy photons of X-rays and γ-rays. Therefore, the super magnetic field and high-energy X-ray and γ-ray of a pulsar are generated not by the neutron star black hole itself, but rather by the high-speed positive ions and free electrons in its accretion disk. When the high-speed rotating pulsar absorbs the adjacent matter to form an accretion disk, its rotation speed slowly decreases. When the rotation speed of the pulsar decreases to a certain speed, even if the pulsar absorbs the matter nearby, it cannot form an accretion disk. Finally, the pulsar evolves into a silent neutron star black hole with only a gravitational field. As dark stars, black holes do not have the so-called determined event horizon, but the supergravity of black holes causes the gravitational redshifts of the magnetic fields and photons that are generated by the high-speed moving charges in the accretion disk. The magnetic field radiation mechanism of the accretion disk also provides a new theory for the study of the origin of the earth's magnetic field.