What Is Rj-11?

By Author: Joseph Brown
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This connector device, an abbreviation for 'Registered Jack', is the standard for the two-pair, or four-wire engineering design for telephone wiring. This type of physical connector interface is the one used most often when wiring telephone terminals. Despite the fact that this connection device features six positions, only two or four of these are usually used. Two standard varieties of RJ-11 connector wiring are available. These include the Unshielded Twisted Pair, or UTP, and the untwisted wiring, also called flat satin cable.

Because nearly every business or residence in North America that uses a single telephone line has this type of jack (typically referred to as POTS jacks) these are the most frequently seen wiring jacks.

The RJ14, which is a jack used for two telephone lines, and the RJ25 device, which is used for three telephone lines, are very similar to the RJ11. Another closely related device that also uses a modular connector with six positions is the RJ61, which can be used for four telephone lines.

Because the RJ11 is usually requires the usage of only two positions, these jacks could be wired ...
... instead with a modular 6P2C jack, which features six positions and two conductors. These jacks, however, are extremely unusual. Most of the time, RJ11 jacks feature four conductors and six positions, and are referred to as 6P4C jacks. When these are used, half of the wires that are connected to the junction box remain unused.

These extra two wires can be used for many different purposes. One example is as a grounding device for certain ringers, or the provision of power to an L.E. D. device known as a ring indicator, which operates from the ringer signal. Alternatively, the wires can be used to inhibit pulse-dial telephones so that they do not ring the 'anti-tinkle' circuit, which is also referred to as the extension phone bells.

To wire an RJ11 jack properly, hold it facing you, so that the contacts point toward the ceiling. The structure of the jack is as follows, with the first color referring to the old color code, and the second color referring to the new:

1. Pin #2 (Black/White containing an orange stripe): Carries either low-voltage alternating current (AC) or direct current (DC) power to the jack from an electric transformer. Also used to power all other jacks in the building.
2. Pin #3 (Red/Blue): Used as the negative terminal for the jack.
3. Pin #4 (Green/White containing a blue stripe): Used as the positive terminal for the jack.
4. Pin #5 (Yellow/Orange): Same as #2 when power is turned on.

Most of the time, sufficient power to the terminals is supplied directly through the telephone line. One exception to this is outdated phone terminals such as the old Western Electric Princess or Trimline telephones, which use incandescent lights. These terminals require more energy than is supplied by telephone lines. This is because their dial lights require approximately 6.3 volts, while the usual output of a transformer is about five volts.