The safety-related SF_TwoHandControlTypeII function block evaluates the switching behavior of a type II two-hand control device connected to the Safety Logic Controller.
It evaluates the switching states of two buttons. The S_TwoHandOut output only becomes SAFETRUE if both inputs switch from SAFEFALSE to SAFETRUE, either simultaneously or consecutively (if both buttons on the two-hand control device are pressed after being not actuated before).
The S_TwoHandOut output switches to SAFEFALSE if one of the inputs is SAFEFALSE or the function block has detected an error. The output can only switch to SAFETRUE again once both inputs are showing the SAFEFALSE state.
Unlike the type III two-hand control device, type II does not evaluate whether both buttons are actuated within a period of 500 ms.
The function block executes stop category 0 at its output.
While function block activation is taking place (with input Activate = TRUE), both inputs must show the SAFEFALSE state. This means that none of the buttons on the two-hand control device must be actuated. Otherwise, the function block detects this as an error (output Error = TRUE, and consequently S_TwoHandOut = SAFEFALSE).
Irrespective of whether there is a single-channel or two-channel connection between the buttons of the two-hand control device and the Safety Logic Controller, both inputs S_Button1 und S_Button2 are only connected to one signal each. When using two-channel buttons, each two-channel signal must be evaluated or monitored as follows:
Either through a suitable upstream safety-related function block, e.g., SF_Equivalent, if the button has two N/C contacts.
Or the evaluation of equivalence or antivalence must be performed in the safety-related input device, also see section "Application example".
Depending on the result of the risk analysis you have performed, you will have to implement cross-circuit detection. When doing so, take into account the relevant information in the online help and in the User Manual for the Safety Logic Controller.