Direct current (DC) is a form of electric energy. Since most wall outlets provide alternating current (AC), the equipment needs to convert the power provided before entering the equipment. A large box transformer will convert power so that the power line can be passed through the DC connector. These connectors come in several different designs. The most common is a simple round plug, but there are also some special styles. Power inverter with DC plug many forms of electronic equipment can only work with DC power, if it is powered by AC power, it will not work, or may have catastrophic failure. On the other hand, AC is a better way to transmit electric energy through the distribution system and home wiring. In order to solve this difference, many devices use transformers in the power system to convert AC to DC. When the power line can be removed from the device, the DC connector is a part of the system. The detachable power cord consists of four parts. The first part is the power cord itself. The AC plug is connected to the wall and uses a standard two prong or three prong connection. If the power cord has a large box, whether it's part of an AC plug or on a wire somewhere, it's a transformer instead of converting AC power to DC power. Some systems have transformers inside the equipment. Finally, the DC connector is opposite to the AC plug, which is directly inserted into the device. The circular metal plug DC connector usually looks like a hollow cylinder. Some circular connectors, commonly known as cylindrical connectors, are just a solid piece of metal. The DC connector is usually an audio device, such as a headset. There is no official specification for these types of connectors, so there are many proprietary designs. Circular DC connectors are the most common, but there are several others. The mini DIN plug is slightly larger than a pencil and has three to ten pins inside, a protective metal case. Miniature din-dc connectors are common in many places, especially in computers and audio / video devices. A separate S-Video connector is a common example of this plug type. Another common non-standard DC connector is Molex connector. These connections are standard four pin leads that can be found on almost every computer's power supply. Molex connector is a standard method of power supply for computer drivers and internal peripherals