IO cards for ABB Symphony Melody


#1

Hi, I am new in field of automation. I need help with binary card CBI20.
datasheet: http://www05.abb.com/global/scot/scot296.nsf/veritydisplay/69deff039b9640eec1256c2c0067ea8e/$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.