Siemens 505-6851A Remote Base Controller

Siemens 505-6851A Remote Base Controller is a stand-alone or redundant RBC used in the SIMATIC TI505‑based 545/555/575 I/O systems to extend remote I/O across RS‑485 to a central Series 505 controller. It enables linking up to 15 additional remote I/O bases, and a remote I/O arrangement can handle 256 discrete inputs and 256 discrete outputs across two remote bases with updates in about 3 milliseconds at a 1 megabaud data rate, ensuring real-time synchronization with the controller’s scan. The 505‑6851A version employs a thumbwheel to set the base address, while the 505‑6851B uses a rotary switch, and the unit provides RS‑232 and I/O ports along with a modem F‑connector for optional dial‑up communications. Power options include a stand‑alone DC supply (PPX:505‑6663) or a redundant 110/220 VAC supply (PPX:505‑6660‑A); the 110/220 VAC supply cannot be used in a redundant configuration. Designed for TI505 controllers, the RBC sits in the remote I/O architecture and supports synchronous updates across remote bases, making it well suited for distributed automation where multiple remote bases must be coordinated from a single controller.