Abstract: A system is disclosed for scanning a keyboard and detecting any depressed key during each scan cycle, and for filtering out any bounce in key contacts closing and opening with a filtering up-down counter that counts up each scan cycle that the same key is found, down each cycle that a different key is also found or that no key is found, and requiring that the filtering counter reach a selected maximum before finding that a key is depressed and that the filtering counter reach zero before starting to filter another key detected to be depressed.