Camera tally system for the raspberry pi

this system is required to detect signal inputs from cables such as the rs232. This must be done on a raspberry pi, and use the java programming language. More information and a basic interface design is shown below. The pi should detect the increase/ decrease in voltages and change the sign accordingly. Please ask if you need more info and additional information is provided in the document attached bellow.
this must be done for the raspberry pi using the java language.

There is more information provided in the document attached. Ask if any further info is required.

Thank you