Siemens Sinumerik 802D sl Instruction Manual page 240

Standards and Approvals
B.5 Safety of electronic control systems
Division into safe and non-safe areas
Nearly all systems contain parts that perform safety-related tasks (e.g. emergency stop
switch, protective grating, two-hand controls). To avoid having to apply safety-related criteria
to the entire controller, it is customary to divide the controller into two areas – one that is
critical to safety and one that is not critical to safety. In the non-safe area of the control
system, no special demands are made, since a failure of the electronics will have no effect
on the safety of the plant. In the safe area, however, only controls and circuits which comply
with the relevant standards and regulations must be used.
Important note
If even a maximum degree of conceptional safety has been achieved when configuring an
electronic control system, e.g. through multichannel design, it is nevertheless imperative to
observe the instructions provided in the relevant instruction manuals exactly; otherwise, im-
proper or incorrect handling could put precautions intended to prevent hazardous errors out
of service or even create additional hazards.
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SINUMERIK 802D sl Instruction Manual (BA), 05/2005 Edition
6FC5 397-0CP10-1BA0