Magnetizers are used to magnetize parts and charge magnets. There are several different types of magnetizing products. Choices include coil magnetizers, electronic capacitance switching (ECS) magnetizers, and yoke magnetizers. Coil magnetizers pass the parts through a magnet, or lay them on top of a magnet. ECS magnetizers allow the user to electronically select the voltage and capacitance require for proper magnetization. This flexibility allows a single piece of equipment to serve as either a small magnetizer or a large magnetizer, depending on the application requirements. Yoke magnetizers are also commonly available. These electromagnets are shaped like horseshoes, and are often used during magnetic-particle testing. Yoke magnetizers work by creating an intense magnetic field between the yoke legs. Magnetic poles are then created at flaws, cracks, or other discontinuities. Magnetizers differ in terms of product specifications. For example, ECS magnetizers have parameters for maximum energy, maximum current, voltage range, capacitance range, and input line power. Weight, dimensions, and the type of output cables required are also important considerations. In terms of features, some ECS magnetizers are designed to sit atop a desk or within a cabinet. Benchtop devices may include capacitor banks that are discharged internally through a safety circuit. Often, the front panel includes an overtemperature interlock circuit to prevent the magnetizer from operating during overheating. An external output allows the user the monitor the magnetic current pulse with an oscilloscope. Product features such as automatic recharging, variable voltage, and solid-state silicon-controlled rectifier (SCR) switching are also available. Magnetizers are used with parts made from a variety of magnetic materials. In terms of their magnetic behavior, these materials can be divided into five classes: diamagnetic, paramagnetic, ferromagnetic, ferrimagnetic, or anti-ferromagnetic. Diamagnetic materials consist of atoms which do not have net magnetic moments. In other words, all of their orbital shells are filled. By contrast, paramagnetic materials include some atoms or ions with partially-filled orbitals and, therefore, some net magnetic moment. Magnetizers for ferromagnetic materials are used with substances such as iron, nickel and magnetite. In these substances, the atomic moments display very strong interactions. For ionic compounds such as oxides, however, crystal structures result in more complex forms of magnetic ordering.