Siemens 6ES5188-3UA12 Simatic S5 Central Rack

Siemens 6ES5188-3UA12 Simatic S5 Central Rack (ZG 135U/155U) is a 21-slot backplane-style rack designed to house SIMATIC S5 central devices within the 135U/155U frame family. It ships with a power supply for AC input 120/230 V and provides a 5 V DC rail, rated at 18 A, while CPU, battery and manual are not included. This central rack serves as the mounting platform and electrical backplane for S5 modules, enabling a compact central controller arrangement in legacy automation systems. The ZG 135U/155U configuration is commonly used to organize CPU modules, I/O cards, and interface modules across up to 21 slots, facilitating the bus connections required by older Siemens S5 installations. As a spare part within the SIMATIC S5 ecosystem, it is encountered in industrial environments that rely on older STEP5-era control logic and requires compatible CPUs and accessories to form a working system.