Siemens Industry Online Support
Siemens AG
Entry type: Application example Entry ID: 109479279, Entry date: 12/16/2015

Two-hand operation to SIL 3 or PL e with a 3SK2 safety relay

  • Entry
  • Associated product(s)

Two-hand operation consoles comprise two pushbuttons that must be pressed simultaneously
to operate a machine. This prevents the operator from reaching into the danger zone during operation.



Operating principle
By imposing the condition of simultaneous pressing of both pushbuttons, the operator is restricted to the two-hand operation console and is thus unable to reach into the danger zone. The 3SK2 safety relay only switches the enabling circuits when both signals are active within 500 ms and the feedback circuit is closed.
If one of the two pushbuttons is released, the 3SK2 safety relay immediately switches the machine off in a safety-related manner.
The four-channel design in the two-hand operation console ensures that possible welding of one of the contacts is detected immediately.
After the emergency stop is actuated, the Start button must be used to restart.

Use of the sensor switch in the two-hand operation console 109479531

 Registrierung notwendig  Project for Safety ES (2,0 KB)

 Registrierung notwendig  Wiring diagrams (51,9 KB) 

 Registrierung notwendig  Project for Safety Evaluation Tool (17,9 KB)

CAx download












Security information
In order to protect technical infrastructures, systems, machines and networks against cyber threats, it is necessary to implement – and continuously maintain – a holistic, state-of-the-art IT security concept. Siemens’ products and solutions constitute one element of such a concept. For more information about cyber security, please visit