The common terminal block is a component that combines the common terminals in one place and saves wiring space. The common terminal is a terminal that can be in communication even when switched to either signal such as on / off, and can support power supply collectively. There are terminal blocks that can be connected simply by inserting cables. The left and right two sets are independent, and the input power supply can have a total of 18 branches. In addition, there are also those that are dedicated to single poles and those that can use the 10 terminals in the upper and lower stages with one unit. There are two types of mounting: a DIN rail mounting type, a direct mounting type, a type that can be mounted on the rail with a single-action by a unitized common, etc. The rated current is mainly 10 A. Since there are various numbers and sizes of commons, it is necessary to select them according to use.