[RQ9.4] The device a SafetyConsumer is running on shall be able to indicate if SAPI.OperatorAckRequested is enabled. This can be done for example by an indicator LED or by using an HMI.

[RQ9.5] If an LED is used for indication, it shall blink in green color with frequency of 0,5 Hz whenever the output SAPI.OperatorAckRequested is true of at least one of the SafetyConsumers running on the device.

NOTE 1 This LED can also be used for other purposes. For instance, a normal operation could be indicated by a non-flashing LED, or erroneous behavior could be indicated by an LED blinking with a frequency higher than 0,5 Hz. Thus, this document does not contain any requirements for the behavior of the LED if SAPI.OperatorAckRequested is false.

The message shown on an HMI is application-specific. For instance, the text “Machine has stopped for safety reasons. For restart, please check for obstacles and press the green button.” could be shown.

NOTE 2 How to realize operator acknowledgment (physical button, element in HMI etc.) is vendor-specific.