Built-in communication port for extension backplanes
Slot spaces are not occupied by Power / CPU / RTU modules
A CPU module and other modules are installed on the main backplane which provides the function of connecting buses. The main backplanes are divided into four types according to the number of I/O modules installed on the main backplanes. These four types are four-slot main backplanes, six-slot main backplanes, eight-slot main backplanes, and twelve-slot main backplanes. Besides, a CPU module installed on the main backplane can be replaced by an RTU module on a control network.