Siemens SIRIUS 3SK1 Manual page 181

Function of the cascading input (terminal INK)
1. Safe combination of safety relays
In this application, a higher-level safety relay switches off the 3SK1 safety relay via the
cascading input via a safe output.
Example:
an EMERGENCY STOP circuit is to deactivate the entire installation as a higher-level
circuit.
Several function groups (e.g., protective doors) that disconnect locally can be operated
as subordinate units.
2. Additional safety sensor circuit
The cascading input INK is ANDed with sensor inputs IN1, IN2 .
PL c in accordance with ISO 13849-1, or SIL1 in accordance with IEC 62061 can be
achieved if the cascading input is wired with single-channel (positive opening) safety
sensors (supply via A1 / +24 V (identical potential to A1)) and if the connecting cable is
laid in a protected fashion. The start function for the cascading input INK corresponds to
the start response of sensor inputs IN1 and IN2 (autostart or monitored start).
The cascading input INK can be triggered with floating or solid-state contact blocks
(switching to P potential). Floating contact blocks must be connected between A1 / +24 V
(identical potential to A1) and the cascading input.
3. Normal switching duty
The cascading input INK can also be used for normal switching duty (not safe). The
cascading input INK can be activated in this case with floating contact blocks or with
solid-state contact blocks (switching to P potential).
Floating contact blocks can be connected between A1 / +24 V and INK .
It is important to note that the start function of cascading input INK corresponds to the
start function of sensor inputsIN1, IN2 .
3SK1 safety relays
Manual, 04/2013, A5E02526190021A/RS-AA/01
WARNING
Application / safety relay safety level
The safety level (PL/SIL) of the application corresponds to the lowest safety level of a
subsystem of the application when errors are excluded (protected wiring of the control
cable).
Configuration / operation
10.2 Explanation of the device's functions
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