16. COMMUNICATING SIGNALS NOTE: The signals prescribed are illustrated by "o" for short Sounds; "-". for longer sounds. SOUND INDICATION (a) o o When standing--start. (b) o o When running--stop at once. (c) o o o When standing--back. (d) o o o When running -- stop at next passenger station. (e) o o o o When standing -- apply or release air brakes. (f) o o o o When running -- reduce speed. (g) o o o o o When standing recall flagman. (h) o o o o o When running --increase speed. (j) o o o o o o When running --increase train heat. (k) - o o o Shut off train heat. (l) - (long) When running -- brakes sticking; look back for hand signals. (n) o o o - Turn on train lights. Unless otherwise provided, each car of a passenger train, when practicable, will be connected with the engine by a communicating signal appliance. When it is inoperative and cannot be put in service without detention, train may proceed after conductor and engineman have an understanding as to how the train is to be operated.