INTRODUCTION TO SONAR 



failure), can prevent vital information from 

 getting through just as effectively as if it were 

 not reported at all. 



Poorly trained or inattentive operators can 

 cause confusion, delay, and mistakes, and may 

 even create a dangerous situation. 



RADIOTELEPHONE 



Radiotelephone (R/T), commonly called voice 

 radio, is a rapid means of exchanging information 

 between ships, aircraft, and submarines. Voice 

 radio usually is amplitude-modulated. A con- 

 tinuous-wave radiofrequency carrier has an audio 

 signal impressed upon it, varying its amplitude 

 in accordance with the audio variations. A handset 

 or a carbon microphone is used to key the trans- 

 mitter. 



Although voice radio is a fast means of com- 

 munication, speed without accuracy is more than 

 worthless — it can be dangerous. Wlien ships are 

 operating together at high speeds and in close 

 formation, a mistake or a delay in communica- 

 tions can cause a collision. 



In antisubmarine operations, voice radio is 

 used to exchange contact and tactical information 

 between the CICs and bridges of the ships 

 participating in the operation. The captain or the 

 OOD mans the bridge radio circuit, used pri- 

 marily to exchange tactical information. The 

 CIC officer and the Radarmen handle the combat 

 information (CI) net to exchange contact informa- 

 tion between CICs. Contact information between 

 CICs is evaluated by the CIC evaluator and 

 pertinent information is relayed to the captain 

 and OOD on the bridge by use of sound-powered 

 phones. 



Because radiotelephone procedures are used 

 with the underwater telephone, and because Sonar 

 Technicians may be assigned CIC watches during 

 normal cruising conditions, it is necessary for 

 you to be familiar with proper radiotelephone 

 procedures. 



RADIOTELEPHONE PROCEDURES 



Whenever you use a radiotelephone, your 

 speech must be clear and slow. Speak the message 

 by natural phrases — not in stilted, word-by-word 

 fashion. Use a normal tone; don't shout. Pro- 

 nounce each word clearly and distinctly, pausing 

 at intervals. Think about what you are going to 

 say, then say it. Keep the message as brief as 

 possible. 



Heading 



The basic format of a military message 

 consists of the heading, text, and ending. The 

 message form is in plaindress, abbreviated 

 plalndress, or codress. Codress is an encrypted 

 message, with which a Sonar Technician normally 

 is not concerned, Plaindress is used for radio- 

 telegraph and teletype communications, as well 

 as for radiotelephone administrative messages. 

 A plaindress message usually has a complex 

 heading, consisting of call, transmission instruc- 

 tions, precedence, date-time group, address, and 

 other elements. The type of radiotelephone mes- 

 s^e you will use most, however, is the abbre- 

 viated plaindress, in which the heading includes 

 only the station called and the station calling. 

 In some instances, after communications are 

 established, the heading contains only the station 

 calling. An example of a typical heading is: 

 FARMERBOY — THIS IS ISLAND QUEEN. 



Text 



The text of the message is the basic thought 

 or idea the originator wishes to communicate. 

 It follows the heading, and is separated from 

 it by the word BREAK. Quite often radiotele- 

 phone messages, particularly those of a tactical 

 nature, are coded. There are several reasons 

 for coding messages. The first is obvious; so 

 that the enemy will not know your intentions. 

 If, for instance, you were ordered in plain 

 language to commence a sonar listening sweep, 

 and the message was intercepted by an enemy 

 submarine, he could rig for silent running to 

 reduce his noise output to a minimum, making 

 your job all the more difficult. If the message 

 is sent in code, however, chances of interpreta- 

 tion by the enemy are reduced even though he 

 should intercept it. Another purpose is brevity. 

 The less time on the air the better, for both 

 security and practical reasons. 



Signal codes are contained in communication 

 publications known as signal books (of which 

 there are several), each having a particular 

 application. One signal book consists of two 

 letters, or a combination of letters and numerals, 

 that usually are used for tactical signals. (Mem- 

 bers of NATO use this book, as well as the 

 standard phonetic alphabet, for combined opera- 

 tions.) As an example, a certain two- letter and 

 a numeral signal tells all ships to make oil fog 

 and smoke. From his signal book, the captain 

 of an Italian ship can read and understand the 



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