Chapter 8 — COMMUNICATIONS 



bridge. The US circuit is the main antisubmarine 

 attack team control circuit. It connects the bridge, 

 CIC, and sonar control, and is used primarily for 

 conning orders when sonar or CIC has control of 

 an attack. Normally, the US is manned by officers 

 in charge of the various stations. 



Circuit discipline must be maintained at all 

 times when you are wearing phones. Personal 

 conversations with friends on the same circuit may 

 cause a delay in the transmission of vital informa- 

 tion, resulting in a delayed or missed attack. With 

 the high speeds of modern submarines, such a 

 delay could result in the loss of your ship or the 

 ship you are trying to protect. 



MC SYSTEMS 



Although sound-powered phones are the most 

 common means of internal communications, there 

 are other methods, one of which is the MC (sliip- 

 board announcing) system. The MC system is an 

 electronic speaker-type system, similar to an 

 office-to-office intercommunication system, and 

 is designed to provide amplified voice communi- 

 cation. 



Sonar and CIC underway watch stations usually 

 are not fully mannedunder normal cruising condi- 

 tions aboard ASW ships. When a sonar contact is 

 gained, the 29MC (sonar control and information) 

 is used to alert CIC, UB plot, and the bridge. 

 Contact Information (such as ranges, bearings, 

 and doppler reports) is passed over this circuit 

 (a one-way system) until the contact is classified 

 as nonsubmarine or until ASW stations can be 

 fully manned. Submarines utilize the 27MC (sonar 

 and radar control) system. 



Another communication system found aboard 

 most slilps and submarines is the 21MC (captain's 

 command system). It is a two-way system, with 

 each intercommunicating unit capable of calling 

 either 10 or 20 stations, depending on the type of 

 ship In which it is installed. The essential 

 components are a reproducer, amplifier, and 

 controls necessary for operation. The reproducer 

 acts as a microphone in the calling unit and as 

 a loudspeaker in the unit called. Amplification 

 takes place in the calling unit. The controls 

 consist of the talk switch, pushbutton assembly, 

 busy light, call light, volume and dimmer controls, 

 and a microphone or handset jackbox. 



To operate the 21MC, depress the pushbutton 

 of the station desired. If the station is busy, the 

 red BUSY light will flash. If the BUSY light does 

 not flash, depress the TALK switch and speak 



directly into the speaker grill. Release the TALK 

 switch to listen. When your conversation is com- 

 pleted, depress the release button at the far left 

 end of the row of station buttons to remove your 

 intercom unit from the circuit. When you are 

 called, the CALL light illuminates. It is unneces- 

 sary to depress the button of the station calling; 

 merely use the TALK switch as described herein. 



Despite its many advantages, when the MC 

 system is used the noise level is increased 

 greatly. Tills condition occurs because of its 

 speaker-type output and the fact that it picks 

 up background noise from the transmitting station. 

 Because of the liigh noise level generated by 

 operating the 21MC, it should be used only when 

 absolutely necessary. 



REMOTE INDICATORS 



The fastest means of communicating informa- 

 tion is to transfer it electi'ically. Through the use 

 of electromechanical and electronic repeaters, 

 sonar information is displayed at remote loca- 

 tions aboard ships and submarines without delay. 



One type of display, an electronic azimuth- 

 range indicator, shows bearing and range of a 

 contact on a cathode ray tube. It duplicates audio 

 and video information present at the sonar 

 operator's console. 



Another type of remote indicator displays 

 sonar information electromechanlcally. Contact 

 range and bearing are shown by counters similar 

 to an automobile's mileage indicator. There is also 

 an electromechanical order transmitter. In tiiis 

 unit, a moving pointer (indicating firing bearing) 

 is matched by the operator at a weapons station. 

 Another moving pointer (indicating course to steer 

 during an attack (is matched on the bridge by the 

 helmsman. 



As you can see, electrical/electronic repeaters 

 reduce the time required to transmit information, 

 eliminate noise-producing transmissions, and 

 reduce the volume of traffic over S/P phone 

 circuits. 



EXTERNAL COMMUNICATIONS 



During antisubmarine operations (and, for that 

 matter, all operations), it is imperative that 

 communications between ASW imlts, such as ships 

 and aircraft, be conducted smoothly and effi- 

 ciently, and free of confusion, insofar as practic- 

 able. A faulty microphone switch of a soimd- 

 powered phone, frequently cutting out (a common 



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