THE WHATIS.COM WORD-OF-THE-DAY October 30, 2001 telephone jacks
______________ TODAY'S SPONSOR: VeriSign - The Internet Trust Company FREE E-COMMERCE SECURITY INFRASTRUCTURE GUIDE When building an e-commerce site, you want to start with a strong, secure foundation. Learn how with VeriSign's FREE White Paper, "Building an E-Commerce Trust Infrastructure." See how you can authenticate your site to customers, use 128-Bit SSL encryption to secure your web servers, and accept secure payments online. Click here: http://ad.doubleclick.net/clk;3499067;5058249;w?http://www.verisign.com/cgi-bin/go.cgi?a=n116955740045000 _____________ TODAY'S WORD: telephone jacks See our definition with hyperlinks at http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214238,00.html In the U. S., telephone jacks are also known as registered jacks, sometimes described as RJ-XX, and are a series of telephone connection interfaces (receptacle and plug) that are registered with the U.S. Federal Communications Commission (FCC). They derive from interfaces that were part of AT&T's Universal Service Order Codes (USOC) and were adopted as part of FCC regulations (specifically Part 68, Subpart F. Section 68.502). The term jack sometimes means both receptacle and plug and sometimes just the receptacle. RJ-11: The most common telephone jack is the RJ-11 jack, which can have six conductors but usually is implemented with four. The RJ-11 jack is likely to be the jack that your household or office phones are plugged into from the ordinary "untwisted" wire (sometimes called "gray satin" or "flat wire") people are most familiar with. In turn, the jacks connect to the "outside" longer wires known as twisted pair that connect to the telephone company central office or to a private branch exchange (PBX). The four wires are usually characterized as a red and green pair and a black and white pair. The red and green pair typically carry voice or data. On an outside phone company connection, the black and white pair may be used for low-voltage signals such as phone lights. On a PBX system, they may be used for other kinds of signaling. Your computer modem is usually connected to an RJ-11 jack. RJ-14: The RJ-14 is similar to the RJ-11, but the four wires are used for two phone lines. Typically, one set of wires (for one line) contains a red wire and a green wire. The other set contains a yellow and black wire. Each set carries one analog "conversation" (voice or data). RJ-45: The RJ-45 is a single-line jack for digital transmission over ordinary phone wire, either untwisted or twisted. The interface has eight pins or positions. For connecting a modem, printer, or a data PBX at a data rate up to 19.2 Kbps, you can use untwisted wire. For faster transmissions in which you're connecting to an Ethernet 10BaseT network, you need to use twisted pair wire. (Untwisted is usually a flat wire like common household phone extension wire. Twisted is often round.) There are two varieties of RJ-45: keyed and unkeyed. Keyed has a small bump on its end and the female complements it. Both jack and plug must match. RELATED TERMS: twisted pair http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci213234,00.html central office http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci211765,00.html private branch exchange http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214278,00.html ___________________ SELECTED LINKS Here's a diagram of the RJ-11 and RJ-45 interfaces. http://www.shout.net/~wildixon/telecom/rj/jackplug.gif _____________________________________ QUIZ #14 | Peripherals FireWire, PCI cards, USB, SCSI...how much do you really know about peripherals? We bet you know more than you think! 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