The output (Q) is enabled after an adjustable delay once the input (Tr) has been switched on.
A rising edge at the input Tr activates the output Q after a duration which is set by the parameter T. The delay time of the block is restarted with each rising edge at Tr. A falling edge at the input Tr switches Q off. If the pulse at Tr is shorter than T then Q will not change state.
When R is then triggered the block timer is reset and the output Q is disabled. Then a new rising edge at the input Tr will activate the output after delay T.
The block can be set to be retentive, this is done by clicking on the battery symbol to set the red NOT dot on the block (input is by default inactive).