Abstract: A locking mechanism of the cylinder type for a business machine wherein four different keys can be accommodated in a single lock to perform various functions or modes of operation. The mechanism includes ring members and locking pins operably associated with the cylinder and with the lock body either to permit or to restrict rotational movement thereof with respect to the ring members. Rotation of a key in the cylinder to a predetermined limit sets up a switching arrangement to provide a signal for each mode of operation desired to be accomplished.