Phoenix Contact PSR-CT Series, Operating Instructions Manual, Page: 53 / 69

Application examples
108366_en_01 PHOENIX CONTACT
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9.2.4 Series connection with mixed startup behavior
Application description
Switch chain The application example shows three PSR-CT safety switches connected in series for mon-
itoring safety equipment. The switch chain is connected to a safety relay. The safety relay
evaluates the signals of the switch chain and switches connected actuators.
Mixed startup behavior The safety relay is wired for operation with autostart.
The first safety switch is equipped with a reset button for manual, monitored start. The other
safety switches are wired for operation with autostart.
If the first safety equipment item is opened and closed again, the safety function expects a
local reset command for the first safety switch. All the other safety switches start automati-
cally after the relevant safety equipment was closed again.
Notes
Phoenix Contact components used
– 3 x PSR-CT safety switch
– Safety relay: PSR-MC40-3NO-1DO-24DC-..
WARNING: Loss of functional safety
Make sure that all safety switches and the safety relay have the same ground potential.
WARNING: Risk due to unexpected machine startup
Cross-circuit between output FOA1 and the cable of the reset button can result in auto-
matic machine startup.
• Avoid cross-circuit between FOA1 and the cable from the reset button by means of
design measures, e.g., protected cable installation.
• See fault exclusion according to EN ISO 13849-2.
Also observe the documentation for all other devices used together with the safety switch.