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A registered jack (RJ) is a standardized telecommunication network interface for connecting voice and data equipment to a service provided by a local exchange carrier or long distance carrier. Registration interfaces were first defined in the Universal Service Ordering Code (USOC) system of the Bell System
Bell System
in the United States for complying with the registration program for customer-supplied telephone equipment mandated by the Federal Communications Commission (FCC) in the 1970s.[1] They were subsequently codified in title 47 of the Code of Federal Regulations
Code of Federal Regulations
Part 68.[2][3][4] The specification includes physical construction, wiring, and signal semantics. Accordingly, registered jacks are primarily named by the letters RJ, followed by two digits that express the type. Additionally, letter suffixes indicate minor variations. For example, RJ11, RJ14, and RJ25
RJ25
are the most commonly used interfaces for telephone connections for one-, two-, and three-line service, respectively. Although these standards are legal definitions in the United States, some interfaces are used worldwide. The connectors used for registered jack installations are primarily the modular connector and the 50-pin miniature ribbon connector. For example, RJ11
RJ11
uses a six-position two-conductor connector (6P2C), RJ14 uses a six-position four-conductor (6P4C) modular jack, while RJ21 uses a 25-pair (50-pin) miniature ribbon connector.

Contents

1 Naming standard 2 History and authority 3 Registered jack
Registered jack
types 4 Similar jacks

4.1 Unofficial plug names 4.2 International use

5 RJ11, RJ14, RJ25
RJ25
wiring

5.1 Pinout 5.2 Provisioning of power

6 RJ21

6.1 Similar connectors

7 RJ45S 8 RJ48 9 RJ61 10 See also 11 References 12 Further reading 13 External links

Naming standard[edit] The registered jack designations originated in the standardization processes in the Bell System
Bell System
in the United States, and describe application circuits and not just the physical geometry of the connectors; inspection of the connector does not necessarily show which registered jack wiring is used. The same modular connector type may be used for different registered jack applications. Strictly, Registered Jack refers to both the female physical connector (modular connector) and its wiring, but the term is often used loosely to refer to modular connectors regardless of wiring or gender, such as in Ethernet
Ethernet
over twisted pair. There is much confusion over these connection standards. The same six-position plug and jack commonly used for telephone line connections may be used for RJ11, RJ14
RJ14
or even RJ25, all of which are names of interface standards that use this physical connector. The RJ11
RJ11
standard dictates a single wire pair connection, while RJ14
RJ14
is a configuration for two lines, and RJ25
RJ25
uses all six wires for three telephones lines. The RJ designations, though, only pertain to the wiring of the jack, hence the name Registered Jack; it is commonplace, but not strictly correct, to refer to an unwired plug by any of these names. Modular connectors were developed to replace older telephone installation methods that used either hardwired cords, or bulkier varieties of telephone plugs. The common nomenclature for modular connectors includes the number of contact positions and the number of wires connected, for example 6P indicates a six-position modular plug or jack. A six-position modular plug with conductors in the middle two positions and the other four positions unused has the designation 6P2C. RJ11
RJ11
uses a 6P2C
6P2C
connector. The connectors could be supplied with more pins, but if more pins are actually wired, the interface is not an RJ11. History and authority[edit] Registration interfaces were created by the Bell System
Bell System
under a 1976 Federal Communications Commission
Federal Communications Commission
order for the standard interconnection between telephone company equipment and customer premises equipment. These interfaces used newly standardized jacks and plugs, primarily based on miniature modular connectors. The wired communications provider (telephone company) is responsible for delivery of services to a minimum (or main) point of entry (MPOE). The MPOE
MPOE
is a utility box, usually containing surge protective circuitry, which connects the wiring on the customer's property to the communication provider's network. Customers are responsible for all jacks, wiring, and equipment on their side of the MPOE. The intent was to establish a universal standard for wiring and interfaces, and to separate ownership of in-home (or in-office) telephone wiring from the wiring owned by the service provider. In the Bell System, following the Communications Act of 1934, the telephone companies owned all telecommunications equipment and they did not allow interconnection of third-party equipment. Telephones were generally hardwired, but may have been installed with Bell System connectors to permit portability. The legal case Hush-A-Phone v. United States (1956) and the Federal Communications Commission's (FCC) Carterfone
Carterfone
(1968) decision brought changes to this policy, and required the Bell System
Bell System
to allow some interconnection, culminating in the development of registered interfaces using new types of miniature connectors. Registered jacks replaced the use of protective couplers provided exclusively by the telephone company. The new modular connectors were much smaller and cheaper to produce than the earlier, bulkier connectors that were used in the Bell System
Bell System
since the 1930s. The Bell System issued specifications for the modular connectors and their wiring as Universal Service Order Codes (USOC), which were the only standards at the time. USOCs are commonly specified to the communications provider by large businesses for a variety of services. Because there are many standardized interface options available to the customer, the customer must specify the type of interface required by RJ/USOC. For a multi-line interface such as the RJ21
RJ21
(which provided 25 pairs), the customer must denote which position(s) of the interface are to be used. If there are multiple RJ21
RJ21
connectors, they are numbered sequentially and the customer must advise the communications provider of which one to use. When the U.S. telephone industry was opened to more competition in the 1980s, the specifications became federal law, ordered by the FCC and codified in the Code of Federal Regulations
Code of Federal Regulations
(CFR), Title 47 CFR Part 68, Subpart F,[2] superseded by T1.TR5-1999.[3] In January 2001, the FCC delegated responsibility for standardizing connections to the telephone network to a new private industry organization, the Administrative Council for Terminal Attachments[4] (ACTA). The FCC removed Subpart F from the CFR and added Subpart G, which delegates the task to the ACTA. The ACTA generates its recommendations for terminal attachments from the standards published by the engineering committees of the Telecommunications Industry Association (TIA). ACTA and TIA jointly published a standard called TIA/EIA-IS-968[5] which contained the information that was formerly in the CFR. The current version of that standard, called TIA-968-A,[5] specifies the modular connectors at length, but not the wiring. Instead, TIA-968-A[5] incorporates a standard called T1.TR5-1999, "Network and Customer Installation Interface Connector Wiring Configuration Catalog",[3] by reference to specify the wiring. With the publication of TIA-968-B,[4] the connector descriptions have been moved to TIA-1096-A.[4] Note that a registered jack name such as RJ11 identifies both the physical connectors and the wiring (pinout) of it (see above). Registered jack
Registered jack
types[edit]

6P4C
6P4C
crimp-on style connector commonly used for RJ11
RJ11
and RJ14

The most widely implemented registered jack in telecommunications is the RJ11. This is a modular connector wired for one telephone line, using the center two contacts of six available positions, and is used for single-line telephones in homes and offices in most countries. RJ14
RJ14
is similar to RJ11
RJ11
but is wired for two lines and RJ25
RJ25
has three lines. RJ61
RJ61
is a similar registered jack for four lines. The RJ45(S) jack is rarely used, but the designation RJ45 commonly refers to any 8P8C modular connector
8P8C modular connector
for application in computer networking (Ethernet). The officially recognized types of registered jacks are listed in the following table:

Code Connector Usage

RJA1X 225A adapter Connector for a modular plug to a four-prong jack

RJA2X 267A adapter Connector for splitting one modular jack to two modular jacks

RJA3X 224A adapter Connector for adapting a modular plug to a 12-prong jack

RJ2MB 50-pin 2–12 telephone lines with make-busy arrangement

RJ11(C/W) 6P2C Establishes a bridged connection for one telephone line ( 6P4C
6P4C
if power on second pair)

RJ12(C/W) 6P6C Establishes a bridged connection for one telephone line with key telephone system control ahead of line circuit

RJ13(C/W) 6P4C Similar to RJ12, but behind the line circuit

RJ14(C/W) 6P4C For two telephone lines ( 6P6C
6P6C
if power on third pair)

RJ15C 3-pin weatherproof For one telephone line for boats in marinas

RJ18(C/W) 6P6C For one telephone line with make-busy arrangement

RJ21X 50-pin Multiple (up to 25) line bridged T/R configuration

RJ25(C/W) 6P6C For three telephone lines

RJ26X 50-pin For multiple data lines, universal

RJ27X 50-pin For multiple data lines, programmed

RJ31X 8P8C Allows an alarm system to seize the telephone line to make an outgoing call during an alarm. Jack is placed closer to the network interface than all other equipment. Only 4 conductors are used.

RJ32X 8P8C Like RJ31X, this wiring provides a series tip and ring connection through the connecting block, but is used when the customer premises equipment is connected in series with a single station, such as an automatic dialer.

RJ33X 8P8C This wiring provides a series tip and ring connection of a KTS line ahead of the line circuit because the registered equipment requires CO/PBX ringing and a bridged connection of the A and A1 lead from behind the line circuit. Tip and ring
Tip and ring
are the only leads opened when the CPE plug is inserted. Typical usage is for customer-provided automatic dialers and call restrictors.

RJ34X 8P8C Similar to RJ33X, but all leads are connected behind the line circuit.

RJ35X 8P8C This arrangement provides a series tip and ring connection to whatever line has been selected in a key telephone set plus a bridged A and A1 lead.

RJ38X 8P4C Similar to RJ31X, with a continuity circuit. If the plug is disconnected from the jack, shorting bars allow the phone circuit to continue to the site phones. Only 4 conductors are used.

RJ41S 8P8C, keyed For one data line, universal (fixed loop loss and programmed)

RJ45S 8P8C, keyed For one data line, with programming resistor

RJ48C 8P4C For four-wire data line (DSX-1)

RJ48S 8P4C, keyed For four-wire data line (DDS)

RJ48X 8P4C with shorting bar For four-wire data line (DS1)

RJ49C 8P8C For ISDN
ISDN
BRI via NT1

RJ61X 8P8C For four telephone lines

RJ71C 50-pin 12 line series connection using 50-pin connector (with bridging adapter) ahead of customer equipment. Mostly used for call sequencer equipment.

Many of the basic names have suffixes that indicate subtypes:

C: flush-mount or surface mount F: flex-mount W: wall-mount L: lamp-mount S: single-line M: multi-line X: complex jack

For example, RJ11
RJ11
comes in two forms: RJ11W is a jack from which a wall telephone can be hung, while RJ11C is a jack designed to have a cord plugged into it. A cord can be plugged into an RJ11W as well. Similar jacks[edit] Unofficial plug names[edit] The following RJ-style names do not refer to official ACTA types:

RJ9, RJ10, RJ22: 4P4C
4P4C
or 4P2C, for telephone handsets. Since telephone handsets do not connect directly to the public network, they have no registered jack code. RJ45: 8P8C, informal designation for T568A/T568B, including Ethernet; not the same as the true RJ45S RJ50: 10P10C, often used for data

International use[edit] The modular jack was chosen as a candidate for ISDN
ISDN
systems. In order to be considered, the connector system had to be defined by an international standard, leading to the creation of the ISO 8877 standard. Under the rules of the IEEE 802
IEEE 802
standards project, international standards are to be preferred over national standards so when the original 10BASE-T
10BASE-T
twisted-pair wiring version of Ethernet
Ethernet
was developed, the modular connector was chosen as the basis for IEEE 802.3i-1990. RJ11, RJ14, RJ25
RJ25
wiring [edit]

6P6C
6P6C
connector showing the location of pin 1

All of these registered jacks are described as containing a number of potential contact positions and the actual number of contacts installed within these positions. RJ11, RJ14, and RJ25
RJ25
all use the same six-position modular connector, thus are physically identical except for the different number of contacts (two, four and six respectively) allowing connections for one, two, or three telephone lines respectively. Cords connecting to an RJ11
RJ11
interface require a 6P2C
6P2C
connector. Nevertheless, cords sold as RJ11
RJ11
often use 6P4C
6P4C
connectors (six position, four conductor) with four wires. Two of the six possible contact positions connect tip and ring, and the other two conductors are unused. The conductors other than the two central tip and ring conductors are in practice variously used for a second or third telephone line, a ground for selective ringers, low-voltage power for a dial light, or for anti-tinkle circuitry to prevent pulse dialing phones from sounding the bell on other extensions. Pinout[edit] Observing the male connector from the cable opening, with prong facing downward, the pins are numbered 1–6, left to right:

Position Pair Tip or Ring ± RJ11 RJ14 RJ25 U.S. Bell System
Bell System
colors[a] 25-pair color code[b] German colors[c] Australian colors Dutch colors[6]

1 3 T +

T3 or white or orange

white/green

violet

orange Not used

2 2 T +

T2 T2

black

white/orange

green

red

orange

3 1 R − R1 R1 R1

red

blue/white

white

blue

red

4 1 T + T1 T1 T1

green

white/blue

brown

white

blue

5 2 R −

R2 R2

yellow

orange/white

yellow

black

white

6 3 R −

R3 or blue or brown

green/white

slate

green Not used

^[a] While the old solid color code was well established for pair 1 and usually pair 2, several conflicting conventions exist for pair 3. The colors are from a vendor of silver-satin flat 8-conductor cable that is claimed to be standard. At least one other vendor of flat 8-conductor cable uses the sequence blue, orange, black, red, green, yellow, brown and white/slate. ^[b] 25-pair color codes established in the 1950s for polyethylene-insulated conductor (PIC) cable.[7] ^[c] This color scheme originates in the national standard DIN 47100 (withdrawn).

Provisioning of power[edit] Some telephones such as the Western Electric Princess and Trimline telephone models require additional power (~6 V AC) for operation of the incandescent dial light. This power is delivered to the telephone set from a transformer by the second wire pair (pins 2 and 5) of the 6P4C
6P4C
connector. RJ21[edit]

Female RJ21
RJ21
connector

Even-count color code

Color Pin (tip)

Pin (ring) Color

White/blue 26

1 Blue/white

White/orange 27

2 Orange/white

White/green 28

3 Green/white

White/brown 29

4 Brown/white

White/slate 30

5 Slate/white

Red/blue 31

6 Blue/red

Red/orange 32

7 Orange/red

Red/green 33

8 Green/red

Red/brown 34

9 Brown/red

Red/slate 35

10 Slate/red

Black/blue 36

11 Blue/black

Black/orange 37

12 Orange/black

Black/green 38

13 Green/black

Black/brown 39

14 Brown/black

Black/slate 40

15 Slate/black

Yellow/blue 41

16 Blue/yellow

Yellow/orange 42

17 Orange/yellow

Yellow/green 43

18 Green/yellow

Yellow/brown 44

19 Brown/yellow

Yellow/slate 45

20 Slate/yellow

Violet/blue 46

21 Blue/violet

Violet/orange 47

22 Orange/violet

Violet/green 48

23 Green/violet

Violet/brown 49

24 Brown/violet

Violet/slate 50

25 Slate/violet

RJ21
RJ21
is a registered jack standard using a modular connector with contacts of up to 50 conductors. It is used to implement a 25-line (or less) telephone connection such as that used in the 1A2 key telephone system. The miniature ribbon connector of this interface is also known as a 50-pin telco connector, CHAMP(AMP), or Amphenol
Amphenol
connector, the latter being a genericized trademark, as Amphenol
Amphenol
was a prominent manufacturer of these at one time. A cable color scheme, known as even-count color code, is determined for 25 pairs of conductors as follows:[8] For each ring, the primary, more prominent color is chosen from the set blue, orange, green, brown, and slate, in that order, and the secondary, thinner stripe color from the set of white, red, black, yellow, and violet colors, in that order. The tip conductor color scheme uses the same colors as the matching ring but switches the thickness of the primary and secondary colored stripes. Since the sets are ordered, an orange (color 2 in its set) with a yellow (color 4) is the color scheme for the 4·5 + 2 − 5 = 17th pair of wires. If the yellow is the more prominent, thicker stripe, then the wire is a tip conductor connecting to the pin numbered 25 + the pair #, which is pin 42 in this case. Ring conductors connect to the same pin number as the pair number. A conventional enumeration of wire color pairs then begins blue (and white), orange (and white), green (and white) and brown (and white), which subsumes a color-coding convention used in cables of 4 or fewer pairs (8 wires or less) with 8P and 6P connectors. Dual Amphenol
Amphenol
connectors are often used on punch blocks to make a breakout box for PBX and other key telephone systems. Similar connectors[edit] The same physical connector is used to connect Ethernet
Ethernet
ports in bulk from a switch with 50-pin ports to a CAT-5
CAT-5
rated patch panel, or between two patch panels. A cable with a 50-pin connector on one end can support 6 fully wired 8P8C
8P8C
connectors or Ethernet
Ethernet
ports on a patch panel with 1 spare pair. Alternatively, only the necessary pairs for 10/100 Ethernet
Ethernet
can be wired allowing 12 Ethernet
Ethernet
ports with a single spare pair. The same connector with spring bail locks is used for SCSI-1 connections. Some computer printers use a shorter 36-pin version known as a Centronics connector.

RJ45S[edit] The RJ45S, a standard[9] jack once specified for modem or data interfaces, uses a mechanically-keyed variation of the 8P8C
8P8C
body with an extra tab that prevents it from mating with other connectors; the visual difference from the more-common 8P8C
8P8C
is subtle. The original RJ45S keyed 8P2C modular connector had pins 5 and 4 wired for tip and ring of a single telephone line, and pins 7 and 8 shorting a programming resistor,[10] [11] [12] but is obsolete today. The RJ45S jack must not be confused with the 8P8C
8P8C
eight-pin modular connector. The latter is often incorrectly called RJ45 connector in several fields such as telecommunications and computer networking but it lacks the extra tab. Besides, its pin-out involves some particular schematics as just mentioned.[13] RJ48[edit]

RJ48C and RJ48X wiring

Pin Pair Signal Color

1 R RX ring Orange/white

2 T RX tip White/orange

3

Reserved White/green

4 R1 TX ring Blue/white

5 T1 TX tip White/blue

6

Reserved Green/white

7

Shield White/brown

8

Shield Brown/white

RJ48
RJ48
is a registered jack. It is used for T1 and ISDN
ISDN
termination and local area data channels/subrate digital services. It uses the eight-position modular connector (8P8C). RJ48C is commonly used for T1 circuits and uses pin numbers 1, 2, 4 and 5. RJ48X is a variation of RJ48C that contains shorting blocks in the jack so that a loopback is created for troubleshooting when unplugged by connecting pins 1 and 4, and 2 and 5. Sometimes this is referred to as a self-looping jack. RJ48S is typically used for local area data channels and subrate digital services, and carries one or two lines. It uses a keyed variety of the 8P8C
8P8C
modular connector. RJ48
RJ48
connectors are fastened to shielded twisted pair (STP) cables, not the standard unshielded twisted pair (UTP) CAT-(1–5).

RJ61[edit] See also: 8P8C
8P8C
and Ethernet
Ethernet
over twisted pair

RJ61
RJ61
wiring (USOC)

Pin Pair Signal Color

1 4 Tip White/brown

2 3 Tip White/green

3 2 Tip White/orange

4 1 Ring Blue/white

5 1 Tip White/blue

6 2 Ring Orange/white

7 3 Ring Green/white

8 4 Ring Brown/white

RJ61
RJ61
is a physical interface often used for terminating twisted pair type cables. It uses an eight position, eight conductor (8P8C) modular connector. This pinout is for multi-line telephone use only; RJ61
RJ61
is unsuitable for use with high-speed data, because the pins for pairs 3 and 4 are too widely spaced for high signaling frequencies. T1 lines use another wiring for the same connector, designated RJ48. Ethernet
Ethernet
over twisted pair (10BASE-T, 100BASE-TX
100BASE-TX
and 1000BASE-T) also use a different wiring for the same connector, either T568A
T568A
or T568B. RJ48, T568A, and T568B are all designed to keep pins close together for pairs 3 and 4. The flat eight-conductor silver-satin cable traditionally used with four-line analog telephones and RJ61
RJ61
jacks is also unsuitable for use with high-speed data. Twisted pair
Twisted pair
cabling must be used with RJ48, T568A
T568A
and T568B. Twisted-pair data patch cable used with the three data standards above is not a direct replacement for RJ61
RJ61
cable, because RJ61
RJ61
pairs 3 and 4 would be split among different patch cable twisted pairs, causing cross-talk between voice lines 3 and 4 that might be noticeable for long patch cables. With the advent of structured wiring systems and TIA/EIA-568-B conventions, the RJ61
RJ61
pinout is falling into disuse. The T568A
T568A
and T568B
T568B
standards are used in place of RJ61
RJ61
so that a single wiring standard in a facility can be used for both voice and data. See also[edit]

Modified Modular Jack – a variation used by Digital Equipment Corporation for serial computer connections BS 6312 – British equivalent to RJ25 EtherCON – ruggedized RJ-45 Ethernet
Ethernet
connector Key telephone system Protea (telephone) – South African telephone jack standard Telecommunications Industry Association – Standards Developing Organization for ACTA Ethernet

References[edit]

^ AT&T, Registration Interface—Selection and General Information, Bell System
Bell System
Practices, Section 463-400-100 Issue 1, May 1976 ^ a b FCC 47 CFR Part 68 Connection of Terminal Equipment to the Telephone
Telephone
Network, Section 68.502 superseded by T1.TR5-1999 ^ a b c T1.TR5-1999 Network and Customer Installation Interface Connector Wiring Configuration Catalog ^ a b c d ACTA documents ^ a b c TIA-968-A
TIA-968-A
or tia-eia-is-968 documents of FCC specifications from the Administrative Council for Terminal Attachments, section 6.2 in particular ^ "(nl) Support document for the 'PTT norm 88'" (PDF). Watel (in Dutch). p. 8.  ^ F.W. Horn, 'Even-Count' Cable, Bell Laboratory Record 37(6), 208 (June 1959) ^ Ogletree, Terry William (2004). "Cables, Connectors, Concentrators, and Other Network Components". Upgrading and Repairing Networks (4 ed.). Que Publishing. p. 84. ISBN 0-7897-2817-6.  ^ http://www.leviton.com/en/support/product-support/network-solutions/wiring-diagrams/usoc-codes ^ http://pe2bz.philpem.me.uk/Comm/-%20Telephone/Site-900-Everything/Plugs/rj45s.html ^ "Modular Jack Wiring". Hamilton Video & Sound Limited. Archived from the original on 2007-10-14. Retrieved 2017-05-21.  ^ "Modular Wiring Reference". Siemon. Retrieved 2010-10-14.  ^ http://www.leviton.com/en/images/USOC_Code_RJ45S.gif

Further reading[edit]

RJ glossary RJ48C, RJ48S, RJ48X T1 & T3 RJ48
RJ48
cables ANSI/ TIA-968-B
TIA-968-B
documents of FCC specifications from the Administrative Council for Terminal Attachments, section 6.2 in particular ANSI/TIA-1096-A John R. Carlsen: On wiring modular telephone connectors Modular wiring reference showing differences between 8P8C, true RJ45 8-position keyed connector, 6P6C, and 6-position modified offset tab Common outlet configurations graphical representation of twisted pair pinouts

External links[edit]

Administrative Council for Terminal Attachments Doing your own telephone wiring Connecting a second phone line

v t e

USOC registered jacks

RJ11 RJ12 RJ14 R

.