This logic group alternately sends a zero and a one to the output.
This realises a flashing.

The cyclic transmitter is controlled via the "Enable" input.
A one on this input activates and a zero deactivates the cyclic transmitter.

The interval time can be changed from 1 to 255 seconds via a separate "Interval" input.
The flashing frequency is defined by the interval time multiplied by 2 (interval time = half flashing period).
The input value "zero seconds" is ignored.