Fail-safe digital output modules are used centrally with SIMATIC S7-31xF-2 DP, and in the ET 200M distributed I/O device together with SIMATIC IM 151-7 F-CPU, S7-31xF-2 DP, S7-416F-2 and S7-400F/FH.

The modules are, for example, suitable for connecting solenoid valves, DC contactors and indicator lights.

In the case of the SM 326 F-DO 10 x DC 24V/2A PP (6ES7 326-2BF10-0AB0), the function "Keep last valid value" can be used optionally in safety mode too. Together with the diagnostics capability of the module, this can be used for cost-optimized implementation of applications in, for example, the area of fire and gas alarm systems (in accordance with EN 54-2/-4 or NFPA72).