External Connectors

CAUTION Figure 2-26.—Wiring harness connector plug (rectangular) assembly. connect to an internal connector receptacle as part of the cabinet wiring harness. NOTE IF A CONDUCTOR MUST BE COMPLETELY OR PARTIALLY REPLACED, REPLACE IT WITH THE SAME GAUGE (AWG) AND TYPE OF CONDUCTOR. SEE THE TECHNICAL MANUAL FOR EXACT ORDERING AND REPLACEMENT INFORMATION. External Connectors The external connectors of a computer are designed to receive electrical power from power sources, send or receive data (input/output) to or from other computers or digital equipment, and to interconnect units of the same computer together. For example, the computer uses external connections to load operational programs and test programs that are stored externally on a magnetic tape unit. It also uses external connections to communicate with other computers or peripherals and/or other systems (display and/or communication). The computer’s prints, wire listings, owner’s manual, CSTOMs, SOMs, and/or systems doctrine or equivalent will provide the exact jack, channel or port, and pins assignments of where power and/or data enter or leave the computer. WHENEVER CONNECTIONS FOR POWER AND DATA ARE DIS- CONNECTED OR RECONNECTED, ENSURE THAT THE POWER TO THE COMPUTER AND THE POWER SOURCE HAVE BEEN SECURED AND THE PROPER TAG-OUT PROCEDURES HAVE BEEN FOLLOWED FOR SECURING THE POWER SOURCE. POWER REQUIREMENTS OF COM- PUTERS. —The power requirements for computers vary. The requirements depend on the type of computer and/or where the computer is used--on ship or ashore. Computers are designed to accept different combina- tions (voltage, frequency, and phase) of primary power. A couple of examples: for a large NTDS computer aboard ship, the requirement is 115 Vat, 400 Hz, 3 phase; whereas, a microcomputer computer ashore uses 115 Vat, 60 Hz, single phase. You need to know the primary power source for your computer system. Become very familiar with the location and operation of your computer’s power source. Know the exact location of power panels in your spaces and know which circuit breakers to secure for routine maintenance and emergency situations. We discuss computer power supplies in chapter 4. EXTERNAL CONNECTOR RECEP- TACLES. —External connector receptacles receive the plug of a cable (conductor). The cables carry power and data. External connector receptacles and their plugs come in all sizes and shapes. Like internal receptacles and plugs, they, too, are keyed or because of their physical shape, can only be mated one way. Power cables and cords are fairly standard. We, therefore concentrate our discussion on some of the I/O connections used for parallel and serial data transfers. The physical shape (architecture) of these connectors does not have anything to do with the standard or the format (parallel or serial) used for the data transferred. Some of the more common series of connectors used for parallel and serial data transfer include the following: Parallel —MIL-C-series—M28840, M38999, and M81511; Centronics Parallel; MTIDC or IDC; “D” series; and Nonstandard series 2-21