IO cards for ABB Symphony Melody

Hi, I am new in field of automation. I need help with binary card CBI20. datasheet:$file/e_10_72_1_31_1_-en_CBI_20-_Binary_input_module.pdf

My question is if CBI20 contains power supply for contacts or not ? I see in datasheet contacts divided to 2 supply group, but what means overvoltage if contacts are supplied from internal power supply ? Thank you.