The ET 200M fail-safe I/Os are used in the redundant design for the distributed expansion of the SIMATIC S7-400FH. Together with the redundant PROFIBUS connection, it is the base of the Flexible Modular Redundancy. This creates the greatest possible availability, because in this way the system can withstand the failure fo a CPU, a PROFIBUS line or a signal module or a combination of different failures.

The fail-safe I/Os are internally redundant, can diagnose internal and external faults and carry out numerous self-tests and field-wiring diagnostics (e.g. short-circuiting, wire-break).

In addition, fail-safe and standard I/O modules (critical and non-critical I/Os) can be combined in one ET 200M/S station.

Benefits of SIMATIC safety I/Os:
	Flexible Modular Redundancy: single, dual and triple I/O-solutions are available
	Safe and standard communication via PROFIsafe (IEC 61508)
	Up to SIL 3, TÜV certified (no: Z2 03 04 38282 002)
	Highest safety level - Self-diagnostics and signal test (short-circuit, wirebreak) without additional programming overhead
	Reduced engineering overhead - Fail-safe shutdown without additional safety relays
	Cost reductions through savings on materials - Coexistence of standard and fail-safe modules in one station
	Space-saving design - Connection of standard and fail-safe I/O using just one PROFIBUS cable

ET 200M overview:

Characteristic: modular I/O module for high-channel applications, with up to 24 channels per module.