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What is the origin of telephone jacks?
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).
What is the most common telephone jack used today?
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 and people are most familiar with. The four wires are usually characterized as a red and green pair and a black and yellow pair. The red and green pair typically carry voice or data. The black and yellow pair may be used for a second line. A computer that uses a dial up modem to connect to a network is usually plugged into an RJ-11 jack. What kind of jack do I need for my two line phone?
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 used for the second line. Each set carries one analog "conversation" (voice or data).
What kind of jack do I need for my DSL line?
The RJ-45 is a single-line jack for digital transmission over ordinary phone wire, either twisted or untwisted. The interface has eight pins or positions. For connecting a modem, printer, or a data connection at a rate up to 19.2 Kbps, you can use untwisted wire. For faster transmissions in which you're connecting to an Ethernet network, you need to use twisted pair wire. To reduce cross talk or FEMF (Foreign Electromagnetic Force) also called induction between pairs of wires.
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