Table  2-2.—  Speed  Light  Signals SIGNAL  SELECTOR SWITCH DIAL MARKINGS PULSATIONS Standard  speed  ahead Steady white light (motor off) One-third  speed  ahead One white flash in 6 seconds Two-thirds  speed  ahead Two white flashes in 6 seconds Full speed ahead Four white flashes in 6 seconds Flank  speed  ahead Five white flashes in 6 seconds Hand pulse key ahead Manually controlled (code same as above) Stop Steady red light (motor off) Slow speed back One flash in 6 seconds Full speed back Two flashes in 6 seconds Hand  pulse  key  back Manually controlled (code same as above) 3.  White  standing  lights  are  used  on  exterior passageways to provide light so the ship's crew may move around the exterior of the ship with out danger of injury. These white standing lights are normally only turned on when the ship is in port or at anchor. INTERIOR COMMUNICATIONS LEARNING OBJECTIVE: Define the purpose and use of the various interior communications systems. Interior communications deal with those forms of communication  between  a  sender  and  a  receiver  aboard the same ship. Interior communications are carried out via sound and some visual methods. Communications by messenger, probably the most ancient of all methods, remains the most reliable system. SHIP'S SERVICE TELEPHONE SYSTEM The ship's service telephone system is similar to a dial  telephone  ashore.  It  is  electrically  powered  and  has a dial apparatus and central switchboard. By means of this system, you can communicate with any part of the ship merely by dialing a number. When the ship is alongside, the ship's service system can be connected with  the  beach  to  permit  outside  calls;  but  the switchboard,  which  functions  automatically  for  interior communications, must be manned by an operator for outside  calls.  Ship's  service  phones  normally  are equipped with light handsets, which are easy to manage, and you do not have to talk any louder or more distinctly than  you  would  on  a  telephone  ashore. An   ordinary   ship's   service   phone,   like   any telephone ashore, sends back a busy signal if it already is in use when dialed. However, if there should be an emergency  call,  some  phones  (such  as  those  on  the bridge or quarterdeck) have an executive right-of-way feature,  by  which  it  is  possible  to  break  into  a conversation  in  progress. The ship's service phone has one disadvantage: The number of talkers it can reach on a single circuit is small compared to the number that can be reached by the sound-powered  battle  phones. SOUND-POWERED-TELEPHONE SYSTEM The battle telephones are sound-powered; that is, instead of a battery or generator, your voice provides the power for the circuit. Failure of the electrical power system has no effect upon the sound-powered phones, although one or more stations can be knocked out by a direct  hit.  You  should  remember  that  every sound-powered receiver is also a transmitter, and vice versa. In other words, if all but one earpiece on a sound-powered headset is knocked out, you normally can continue to both talk and receive through the earpiece. 2-15