The board has 2 banks of input that could be handled independently and isolated from each other and from the board.
Each bank of inputs has bidirectional inputs which activate with a voltage between +5vdc and +24vdc.
If the signals that you want to activate the input negative (Open Collector), you would need to feed +5vdc or +24vdc into the COM port of the input bank you are using (COM1 or COM2) and if the signals are positive, then you need to feed the negative of the power supply to the COM and +5vdc (TTL) or +24vdc will activate the input.
There are LEDs on all the inputs which light when the input is activated.