The traffic control system shown below has INPUTS and OUTPUTS. Each input and output has a number - these are listed on the diagram below.

Write the control sequence for the following sequence of events: Please note, when the barrier is raised/open it is ‘ON’. When the barrier is lowered/closed it is ‘OFF’. The first five stages have already been completed.

IMPROVEMENT 1: The system should have an audible (sound) warning as well. This would allow the drivers to hear as well as see warnings that the barrier is about to be closed.

IMPROVEMENT 2: The system should have two sensors that detect the presence of trains. This would mean that the system would work safely even if one of the sensors failed.