SYSTEMS EQUIPMENT AND LOCATION

A voice switch self-test and fault location read- out (built-in test). An audio indication to the user when the voice switch built-in-test (BIT) detects a trunk line short. A technical control monitor phone, incorpo- rated into the voice switch, which can access all voice channels. SYSTEMS EQUIPMENT AND LOCATION The following paragraphs provide a brief description of the major equipment included in a typical SAS installation. Figure 2-13 illustrates the audio path of the system and the order in which we will discuss the equipment. User Station Equipment User station equipment is located in operations centers throughout the ship, like the bridge, combat information center (CIC), flag plot, secondary corm, and other stations where exterior voice com- munications are required by the ship’s mission. This equipment consists of telephone sets, audio amplifiers, loudspeakers, headsets, recorders, audio jackboxes, Naval Tactical Data System (NTDS) consoles and intercom units, and local switching devices for added system flexibility. Voice Switching Equipment The voice switching equipment is a major component of the SAS. It is the interface and primary switch between the user’s equipment and all crypto and plain subsystems. It is designed for very high interchannel isolation, which is a TEMPEST requirement for all equipment that handle both secure and nonsecure signals at the same time. (The ASAS and MSAS use different switches for this purpose.) Crypto and Plain Subsystems The various crypto and plain subsystems are located in the main communications spaces. Cryptographic devices and other “red” equipment are located in a secure area within these spaces. There are five crypto and plain subsystems used within the SAS: NESTOR, VINSON, PARKHILL, FLTSATCOM secure voice, and PLAIN ONLY. Additional classified information on these subsystems is available on a need-to-know basis. Transmitter and Receiver Transfer Switchboards These equipment are part of the overall exterior communications switching system and are located in the main communications spaces, generally in the vicinity of the technical control working area. The switchboard equipment group interconnects crypto and plain subsystem equipment with the appropriate radio equipment. You should recall from chapter 1 that these switchboards are also the interconnecting points for other subsystems within the overall exterior communications system. Therefore, they are not unique to the SAS. Transmit and Receive Radio Equipment These equipment may be located in both the main communications spaces and in separate rooms located in various parts of the ship. This equipment group consists of the various transceivers, transmitters, and receivers used for voice nets. The more common transceivers you will encounter are the AN/SRC-20 series, AN/VRC-46, AN/WSC-3(V)3 and (V)7, AN/URC-93, and AN/WSC-6. Common transmitters include the AN/URT-23, AN/URT-24, T-1322/SRC, and AN/GRT-21. Common receivers are the R-1051 series, R-1903, and AN/GRR-23. For additional information on individual equipment, refer to that equipment’s technical manual. TELETYPEWRITER/FACSIMILE EQUIPMENT In chapter 1, we discussed different methods of voice communications. Sometimes, the message is too long for practical transmission by voice, so to get your message or idea across, you may need to use a chart, map, or photograph. Teletype (tty) and facsimile (FAX) equipment allow us to do this. In the following paragraphs, we will discuss some common terms associated with tty and FAX equipment. We will then look at some basic systems. MODES OF OPERATION There are two basic modes of teletypewriter operation: asynchronous (start-stop) and synchronous. The asynchronous mode is the most common. The synchronous mode is used primarily in high-speed data systems. Asynchronous Mode In this mode, the receiving device is only allowed to run for one character and is then stopped to await the start signal for the next character. Any differences in speed between the transmitting and receiving devices can only accumulate during the time assigned to one 2-15