 The "spacing" condition of a current loop line is indicated by no current flowing, and a very long period of no current flowing is often caused by a break or other fault in the line.Some equipment will deliberately transmit the "space" level for longer than a character as an attention signal.When signaling rates are mismatched, no meaningful characters can be sent, but a long "break" signal can be a useful way to get the attention of a mismatched receiver to do something (such as resetting itself).