The STO and SBC functions can be used for implementing the category 0 emergency stop function according to IEC 60204-1:2016.
The Emergency stop function can be realized
With an emergency stop switch connected directly to control the STO-SBC input signals
With an emergency stop relay + emergency stop switch.
With safety PLC + emergency stop switch.
Please read the section about the working principle of the Safety circuit.
All cases above require correct behaviour from the controlling PLC. After releasing the emergency stop device, a separate and deliberate action must be used to restart the system (restarting can be done with a non-safety PLC).
IEC 60204-1:2016 requires “reset shall not initiate a restart” regarding emergency stop.