View source for Modular connector

{{short description|Electrical connector commonly used in telephone and computer networks}}
{{Use American English|date=December 2019}}

[[File:rjxx.jpg|thumb|Left to right, modular connectors: 8P8C plug, 6P6C plug, 6P4C plug, 4P4C plug, 6P6C jack.]]
[[File:Uncrimped rj-45 connector close-up.jpg|thumb|An 8P8C modular plug. This is the common crimp-type plug, of the same kind pictured above [[Crimp (joining)|crimped]] onto a cable (with molded sleeve).]]

A '''modular connector''' is a type of [[electrical connector]] for cords and cables of electronic devices and appliances, such as in [[computer network]]ing, telecommunication equipment, and audio headsets.

Modular connectors were originally developed for use on specific [[Bell System]] telephone sets in the 1960s, and similar types found use for simple interconnection of customer-provided telephone subscriber premises equipment to the telephone network. The [[Federal Communications Commission]] (FCC) mandated in 1976 an interface registration system, in which they became known as [[registered jack]]s. The convenience of prior existence for designers and ease of use led to a proliferation of modular connectors for many other applications. Many applications that originally used bulkier, more expensive connectors have converted to modular connectors. Probably the best-known applications of modular connectors are for [[Telephone line|telephone]] and [[Ethernet]].

Accordingly, various electronic interface specifications exist for applications using modular connectors, which prescribe physical characteristics and assign electrical signals to their contacts.

==Nomenclature==
Modular connectors are often referred to as ''modular phone jack and plug'', ''RJ connector'', and ''Western jack and plug''.  The term ''modular connector'' arose from its original use in modular wiring components of telephone equipment by the [[Western Electric Company]] in the 1960s.<ref name=krumreich /> This includes the [[#6P2C|6P2C]] used for [[Telephone jack and plug|telephone line connections]] and [[#4P4C|4P4C]] used for [[handset]] connectors.

[[Registered jack]] designations describe the signals and wiring used for voice and data communication at customer-facing interfaces of the [[public switched telephone network]] (PSTN). It is common to use a registered jack number to refer to the physical connector itself; for instance, the regular 8P8C modular connector type is often labeled ''RJ45'' because the registered jack standard of the similar name ''RJ45S'' specified a similar, but modified, 8P8C modular connector. Similarly, various six-position modular connectors may be called ''RJ11''. Likewise, the 4P4C connector is sometimes called ''RJ9'' or ''RJ22'' though no such official designations exist.{{Citation needed|date=October 2021|reason=Please cite references to RJ9 and RJ22.}}

==History==
The first types of small modular telephone connectors were created by AT&T in the mid-1960s for the plug-in handset and line cords of the [[Trimline]] telephone.<ref name=krumreich>Krumreich C.L., Mosing L.W., ''The Evolution of a Telephone'', Bell Laboratories Record 44(1) p.14 (January 1966)</ref> Driven by demand for multiple sets in residences with various lengths of cords, the Bell System introduced customer-connectable part kits and telephones, sold through ''PhoneCenter'' stores in the early 1970s.<ref>Walden S.W., ''Telephone Sets Go Mod (Modular, That Is)'', Bell Laboratories Record, Vol. 52(8) p. 238 (Sept. 1974)</ref> For this purpose, Illinois Bell started installing modular telephone sets on a limited scale in June 1972. The patents by Edwin C. Hardesty and coworkers, {{patent|US|3699498}} (1972) and {{patent|US|3860316}} (1975), followed by other improvements, were the basis for the modular molded-plastic connectors that became commonplace for telephone cords by the 1980s. In 1976, these connectors were standardized nationally in the United States by the Registration Interface program of the [[Federal Communications Commission]] (FCC), which designated a series of Registered Jack (RJ) specifications for interconnection of customer-premises equipment to the PSTN.<ref>AT&T, ''Registration Interface—Selection and General Information'', Bell System Practices, Section 463-400-100 Issue 1, May 1976</ref><ref name=FCC47Part68>[http://www.tscm.com/FCC47CFRpart68.pdf FCC 47 CFR Part 68 ''Connection of Terminal Equipment to the Telephone Network''], Section 68.502 superseded by T1.TR5-1999</ref>

==Gender==
Modular connectors have [[Gender of connectors and fasteners|gender]]: ''plugs'' are considered to be ''male'', while ''jacks'' or ''sockets'' are considered to be ''female''. Plugs are used to terminate cables and cords, while jacks are used for fixed locations on surfaces of walls, panels, and equipment.  Other than telephone extension cables, cables with a modular plug on one end and a jack on the other are rare. Instead, cables are usually connected using a female-to-female coupler, having two jacks wired back-to-back.

==Latching tab and orientation==
Most modular connectors are designed with a latching mechanism that secures the physical connection.  As a plug is inserted into a jack, a plastic tab on the plug locks against a ridge in the socket so that the plug cannot be removed without disengaging the tab by pressing it against the plug body. The standard orientation for installing a jack in a vertical surface is with the tab down.

The modular plug is often installed with a ''boot'', a plastic covering over the tab and body, to prevent the latching tab from hooking into other cords or edges, which may cause excessive bending or breaking of the tab. Such '''{{visible anchor|snagless}}''' cords are usually constructed by installing the protective boot before the modular plug is crimped.

==Size and contacts==
[[File:Rj45plug-8p8c.png|thumb|8P8C modular plug contact numbering]]

Modular connectors are designated using two numbers that represent the maximum number of contact positions and the number of installed contacts, with each number followed by ''P'' and ''C'', respectively. For example, ''6P2C'' is a connector having six positions and two installed contacts. Alternate designations omit the letters while separating the position and contact quantities with either an ''x'' (''6x2'') or a slash (''6/2'').

When not installed, contacts are usually omitted from the outer positions inward, such that the number of contacts is almost always even. The connector body positions with omitted or unconnected contacts are unused for the electrical connection but ensure that the plug fits correctly. For instance, inexpensive telephone cords often have connectors with six positions and four contacts, to which are attached just two wires, carrying only line 1 from a one-, two-, or three-line [[Registered jack#RJ11, RJ14, RJ25 wiring|jack]].

The contact positions are numbered sequentially starting from 1. When viewed head-on with the retention mechanism on the bottom, jacks will have contact position number 1 on the left and plugs will have it on the right. Contacts are numbered by the contact position. For example, on a six-position, two-contact plug, where the outermost four positions do not have contacts, the two contacts are numbered 3 and 4.

Modular connectors are manufactured in four sizes, with four, six, eight, and ten positions. The insulating plastic bodies of 4P and 6P connectors have different widths, whereas 8P or 10P connectors share an even larger body width.

===Insulation displacement contact types===
<gallery>
Rj-45 male compare.jpg|8P8C plug with contacts for solid wire (left) and stranded wire (right)
Rj-45 male compare 2.jpg|Contacts for solid wire (top left) and stranded wire (bottom right)
</gallery>

Internally, the contacts in the plugs have sharp prongs that, when [[Crimp (joining)|crimped]], displace the wire insulation and connect with the conductors inside—a mechanism known as [[insulation displacement]]. Cables have either solid or stranded ([[tinsel wire]]) conductors, and a given plug is designed for only one type. The sharp prongs are different in the connectors made for each type of wire, and a mismatch between plug type and wire type results in unreliable connections. A modular plug for solid (single-strand) wire often has three slightly splayed prongs on each contact to securely surround and grip the conductor while scraping along the outside, and a plug for stranded wire has prongs that are designed to pierce the insulation and go straight through to contact multiple wire strands.

=== Interchangeability ===
Some modular connectors are ''indexed'', meaning their dimensions are intentionally non-standard, preventing connections with connectors of standard dimensions. The means of indexing may be non-standard cross-sectional dimensions or shapes, retention mechanism dimensions or configuration. For example, a [[Modified Modular Jack]] using an offset latching tab was developed by [[Digital Equipment Corporation]] to prevent accidental interchange of data and telephone cables.

{|class="wikitable" style="float:right;"
|+Modular connector typical dimensions (millimeters)
|-
!Connector
!Length
!Width
!Height
|-
|4P4C{{citation needed|date=May 2019}}
|
|7.7
|
|-
|6P6C<ref>{{cite web |title=Six Conductor/Six Position Line Cord Module |url=https://belfuse.com/resources/drawings/stewartconnector/dr-stw-940-sp-3066r.pdf |website=Bel-Stewart Connector |publisher=Bel |access-date=3 August 2021}}</ref>
|13.34
|9.85
|6.60
|-
|8P8C<ref>{{cite web |title=RJ-45 Plug for Proposed CAT 6 Specifications |url=https://www.molex.com/pdm_docs/sd/449150001_sd.pdf |website=Molex #449150001, Modular Plug, Category 6, Long Body, Unshielded, 8/8 |publisher=Molex, LLC |access-date=3 August 2021}}</ref>
|22.48
|11.68
|8.00
|}

The dimensions of modular connectors are such that a narrower plug can be inserted into a wider jack that has more positions than the plug, leaving the jack's outermost contacts unconnected. The height of the plug's insertion area is 0.260&nbsp;inches (6.60&nbsp;mm) and the contacts are 0.040&nbsp;inches (1.02&nbsp;mm) apart (contact pitch), so the width is dependent on the number of pin positions.<ref>{{cite web |title=Six Conductor/Six Position Line Cord Module |url=https://belfuse.com/resources/drawings/stewartconnector/dr-stw-940-sp-3066r.pdf |website=Bel-Stewart Connector |publisher=Bel |access-date=3 August 2021}}</ref><ref>{{cite web |title=RJ-45 Plug for Proposed CAT 6 Specifications |url=https://www.molex.com/pdm_docs/sd/449150001_sd.pdf |website=Molex #449150001, Modular Plug, Category 6, Long Body, Unshielded, 8/8 |publisher=Molex, LLC |access-date=3 August 2021}}</ref> However, not all plugs from all manufacturers have this capability, and some jack manufacturers warn that their jacks are not designed to accept smaller plugs without damage. If an inserted plug lacks slots to accommodate the jack's contacts at the outermost extremes, it may permanently deform the outermost contacts of an incompatible jack.  Excessive resistance may be encountered when inserting an incompatible plug, as the outermost contacts in the jack are forcibly deformed.

Special modular plugs have been manufactured (for example, the [[The Siemon Company|Siemon]] UP-2468<ref>{{cite web|url=http://www.siemon.com/e-catalog/ECAT_GI_page.aspx?GI_ID=mpc_universal-modular-plug|title=Universal Modular Plug}}</ref>) which have extra slots beyond their standard contacts, to accommodate the wider jack's outermost contacts without damage.  These special plug connectors can be visually identified by carefully looking for the extra slots molded into the plug.  The molded plastic bodies of the special plugs may also be colored with a light blueish tinge to aid in quick recognition. The special plugs are preferred for test equipment and adapters, which may be rapidly connected to a large number of corresponding connectors in quick succession for testing purposes. The use of the special plugs avoids inadvertent damage to the equipment under test, even when a narrower plug is inserted into a nominally incompatible wider jack.

==Termination==
[[File:Crimping-pliers-pro-RJ-0a.jpg|thumb|right|A modular plug crimping tool with exchangeable crimping dies]]

Termination of cables with modular connectors is similar across the various number of positions and contacts in the plug. The crimping tool contains a die that is often exchangeable and is closely matched to the shape and pin count of the modular plug.

A crimping die-set looks similar to an 8P8C jack, except for the eight teeth lining the top portion of the die. When the tool is operated, the die compresses around the 8P8C plug.  As the die compresses, these teeth force the plug contacts into the conductors of the cable being terminated. The crimper may also permanently deform part of the plastic plug body in such a way that it grips the outer sheath of the cable for secure fastening and [[strain relief]]. These actions permanently attach the plug to the cable.

==Pinout==
The contact assignments ([[pinout]]) of modular connectors vary by application. Telephone network connections are standardized by registered jack designations, and [[Ethernet over twisted pair]] is specified by the [[ANSI/TIA-568]] standard. For other applications, standardization may be lacking; for example, multiple conventions exist for the use of 8P8C connectors in [[RS-232]] applications. For this reason, [[D-sub]]-to-modular adapters are typically shipped with the D-sub contacts (pins or sockets) terminated but not inserted into the connector body so that the D-sub-to-modular contact pairing can be assigned as needed.

==4P4C==
[[File:RJ9.jpg|thumb|right|4P4C modular connector on a handset cord.]]
[[File:ATTtelephone-large.jpg|thumb|right|Wired telephone that uses 4P4C connectors for the coiled handset cord]]

The four-position four-conductor ('''4P4C''') connector is the standard modular connector used on both ends of telephone [[handset]] cords and is therefore often called a ''handset connector''.<ref>{{cite book | author = BICSI | title = Telecommunications Cabling Installation | edition = 2nd | date = October 7, 2002 | publisher = [[McGraw-Hill Professional]] | isbn = 0-07-140979-3 | page = 88 | chapter = Background Information | quote = 4-position and 4-contact connectors are used primarily for telephone handset cords.}}</ref>

This handset connector is not a registered jack, because it was not intended to connect directly to telephone lines. However, it is often referred to as ''RJ9'', ''RJ10'', or ''RJ22''.

===Handset wiring===
[[File:RJ9 Handset diagram.svg|Wiring diagram of 4P4C/RJ9 connector in telephone handset cord]]

Handsets and often [[Headset (audio)|headsets]] for use with telephones commonly use a 4P4C connector. The two center pins are commonly used for the receiver, and the outer pins connect the transmitter so that a reversal of conductors between the ends of a cord does not affect the signal routing. This may differ for other equipment, including hands-free headsets.

===Data port===
The [[Macintosh 128K]], [[Macintosh 512K]] and [[Macintosh Plus]] from [[Apple Inc.|Apple]] as well as the [[Amiga 1000]] from [[Commodore International|Commodore]] use 4P4C connectors to connect the keyboard to the main computer housing.  The connector provides power to the keyboard on the outer two contacts and receives data signals on the inner pair. The cable between the computer and the keyboard is a coiled cord with an appearance very similar to a telephone handset cable.<ref>{{Citation | url = http://www.myoldcomputers.com/museum/comp/plus.htm | title = My Old Computers | contribution = Apple Macintosh Plus | access-date = 2010-10-16 | archive-url = https://web.archive.org/web/20090227062010/http://myoldcomputers.com/museum/comp/plus.htm | archive-date = 2009-02-27 | url-status = dead }}.</ref> The connector on the Amiga 1000 uses crossover wiring, similar to a telephone handset. The connector wiring on the Apple computers, however, requires a polarized straight-through pinout. Using a telephone handset cable instead of the supplied cable could short out the +5 volt DC supply and damage the Apple computer or the keyboard.<ref>{{Citation | publisher = Megadon | url = http://www.megadon.co.uk/wb/whiteboardshow.pl/syrinx/wbfile=Mac%20Plus%20Keyboard%20Cable.wb/page=default.html | title = Syrinx | contribution = Mac Plus Keyboard Cable | place = UK | quote = ...the cable is the same as the telephone cable that connects handsets to the phone, unfortunately [...] this type of cable and pretty much any type of pre manufactured cable [...] is wired wrong for the Mac Plus. Under no circumstances should you use this cable as you will damage your keyboard and/or your Mac!}}</ref>

Modular connectors are often used for data links, such as serial line connections, because of their compact dimensions. For example, some [[DirecTV]] set-top boxes include a 4P4C data port with an adapter cord to connect to a computer serial port to control the set-top box.<ref name=DirecTV>{{cite web | url = http://www.gbpvr.com/pmwiki/pmwiki.php/Utility/DirecTVChannelControl | publisher = [[GB-PVR]] | type = wiki | title = Direc TV Channel Control | quote = Each end of a handset cord is wired opposite the other... |archive-url=https://web.archive.org/web/20081019191930/http://www.gbpvr.com/pmwiki/pmwiki.php/Utility/DirecTVChannelControl |archive-date=2008-10-19 |url-status=dead}}</ref>

==6P {{anchor|6P6C|6P4C|6P2C}} ==<!-- Redirect target for [[6P6C]], [[6P4C]], [[6P2C]] -->
[[File:Conector RJ11.jpg|thumb|6P4C crimp-on–style connector]]
Modular plugs are described by the maximum number of physical [[Electrical connector|contact]] positions and the actual number of contacts installed in these positions. The '''6P2C''', '''6P4C''', and '''6P6C''' modular connectors are probably best known for their use as [[RJ11]], [[RJ14]], and [[RJ25]] non-powered registered jacks, respectively (and 6P4C and 6P6C for powered RJ11 and RJ14, power being delivered on the outer pairs). These interfaces use the same six-position modular connector body but have different numbers of pins installed.

RJ11 is a jack, a physical interface, by definition used for terminating a single telephone line. RJ14 is similar, but for two lines, and RJ25 is for three lines. [[RJ61]] is a similar registered jack for four lines, but uses 8P8C connectors.

===RJ11 wiring===
Cables sold as ''RJ11'' (the name of a single-jack, not a cable) often actually use 6P4C connectors (six positions, four contacts). Two of its six possible contact positions connect [[tip and ring]] of a single telephone line, and the other two contact positions may be unused, carry a second line, or provide low-voltage power for night light or other features on the telephone set. In some installations, an extra contact was also required for the [[ground (electricity)|ground]] connection for [[Party line (telephony)|selective ringers]].

===Pinout===
The pins of the 6P6C connector are numbered 1 to 6, counting left to right when holding the connector tab side down with the opening for the cable facing the viewer.
<!-- To edit this table go to: https://en.wikipedia.org/wiki/Template:Registered_jack -->
{{Registered jack}}
However, with German domestic telephone equipment, and that in some neighboring countries, [[6P4C]] plugs and sockets are typically only used to connect the telephone cord to the phone base unit, whereas the mechanically different [[TAE connector]] is used at the other end to connect to a service provider interface. Older base units may accommodate the additional connectors of TAE (E, W, a2, b2) and may feature non-RJ standard sockets that can be connected directly to TAE plugs.  Further, flat DIN 47100 cables typically place the wires in ascending order.  When used directly with 6P4C plugs, the color coding may be undetermined.

===Powered version of RJ11===
In the powered version of the RJ11 interface, pins 2 and 5 (black and yellow) may carry low-voltage AC or DC power. While the telephone line on pins 3 and 4 (red and green) supplies enough power for most telephone terminals, old telephone terminals with incandescent lights, such as the Western Electric [[Princess telephone|Princess]] and [[Trimline telephone]]s, need more power than the phone line can supply. Typically, the power on pins 2 and 5 is supplied by an [[AC adapter]] plugged into a nearby power outlet which potentially even supplies power to all of the jacks in the house.

===Compatibility with structured cabling===
[[Structured cabling]] networks adhering to [[ANSI/TIA-568]], [[ISO/IEC 11801]] (or ISO/IEC 15018 for home networks) are widely used for both computer networking and analog telephony. These standards specify the T568A or T568B wiring arrangements compatible with [[Ethernet]]. The 8P8C jack used by structured cabling physically accepts the 6-position connector that fits RJ11, RJ14 and RJ25. Only lines 1 and 2 have electrical compatibility, with T568A wiring, and only line 1 with T568B wiring, because Ethernet-compatible pin assignments split the third pair of RJ25 across two separate cable pairs, rendering that pair unusable by an analog phone. (With T568B wiring, a telephone may connect to line 3 as ''line 2''.) Both the third and fourth pairs of RJ61 are similarly split. The incompatible T568A and T568B layouts were necessary to preserve the electrical properties of the third and fourth pairs for Ethernet, which operates at much higher frequencies than analog telephony. Because of these incompatibilities, and because RJ25 and RJ61 were never very common, the T568A and T568B conventions have largely displaced RJ25 and RJ61 for telephones with more than two lines.

==8P8C {{anchor|8P}} ==
[[File:Uncrimped rj-45 connector close-up.jpg|thumb|right|An 8P8C modular plug not yet [[Crimp (joining)|crimped]] onto a cable]]
[[File:RJ45 female connector.jpg|thumb|An 8P8C female modular connector with a key cut (the connector used in the obsolete RJ45S specification)]]

The '''8 position 8 contact''' ('''8P8C''') connector is a modular connector commonly used to terminate [[twisted pair]] and multi-conductor [[flat cable]]. These connectors are commonly used for [[Ethernet over twisted pair]], registered jacks and other telephone applications, [[RS-232]] serial communication using the [[ANSI/TIA-568]] (formerly TIA/EIA-568) and [[Yost cable|Yost]] standards, and other applications involving [[unshielded twisted pair]], [[shielded twisted pair]], and multi-conductor flat cable.

An 8P8C modular connection consists of a male plug and a female jack, each with eight equally spaced contacts. On the plug, the contacts are flat metal bars positioned parallel to the connector body. Inside the jack, the contacts are metal spring wires angled away from the insertion interface. When the plug is mated with the jack, the contacts meet and create an electrical connection. The spring force of the jack contacts ensures a good interface.

[[File:8P8C vs RJ45 female connectors.png|thumb|'''Left''': Generic 8P8C (or 8PMJ, 8-position modular jack) male connector. '''Right''': 8P8C male connector with key, which mates with RJ41S, RJ45S, and RJ48S]]

Although commonly referred to as '''RJ45''' in the context of Ethernet and [[structured cabling]], ''RJ45'' originally referred to a specific wiring configuration of an 8P8C female connector.{{Sfn | Trulove | 2005 | pp = 23, 132 | ps =: ''Designing LAN Wiring Systems'': The 8-pin modular jack is sometimes referred to as an "RJ-45", because the connector/jack components are the same. However, RJ-45 actually applies to a special purpose jack configuration that is not used in LAN or standard telephone wiring. […] ''Work Area Outlets'': Modular jacks are often referred to as "RJ-45" jacks. This is not really the correct moniker, although it is in very common use.}}<ref>{{cite book | last1 = Oliviero | first1 = Andrew | last2 = Woodward | first2 = Bill | title = Cabling: The Complete Guide to Copper and Fiber-Optic Networking | edition = 4th | date  = July 20, 2009 | publisher = [[Sybex]] | isbn = 978-0-470-47707-6 | page = 294 | chapter = Connectors | quote = The RJ (registered jack) prefix is one of the most widely (and incorrectly) used prefixes in the computer industry; nearly everyone, including people working for cabling companies, is guilty of referring to an eight-position modular jack (sometimes called an 8P8C) as an RJ-45.}}</ref><ref>{{cite book | last1 = Semenov | first1 = Andrey B. | last2 = Strizhakov | first2 = Stanislav K. | last3 = Suncheley | first3 = Igor R. | title = Structured cable systems | date = October 3, 2002 | publisher = [[Springer Science+Business Media|Springer]] | isbn = 3-540-43000-8 | page = 129 | chapter = Electrical Cable Connectors | quote = The traditional 8-contact connector, which is called Western Plug, 8PMJ (8-position modular jack), 8P8C (8 position 8 conductor), or somewhat incorrectly RJ-45, is used widely in SCS practice.}}</ref> The original telephone-system-standard RJ45 plug has a key that excludes insertion in an un-keyed 8P8C socket.{{Sfn | Trulove | 2005 | p = 219 | ps =: ''User Cords and Connectors'': This 8-pin modular plug is probably the most subject to name abuse, because it resembles the specialized RJ-45 connector. However, the RJ-45 wiring pattern (which includes an interface programming resistor) is so radically different from that of T568A and B that it really should not be called by that name at all.}}

The original RJ45S{{efn|The often omitted ''S'' suffix indicates this is a wiring configuration supporting a single telephone line.}} was intended for high-speed modems and is obsolete. The RJ45S jack mates with a keyed 8P2C modular plug,<ref name="HVS">{{citation | url = http://www.hvs.on.ca/modular_jack_wiring.htm | publisher = HVS | location = Ontario, California | title = Modular jack wiring | url-status = dead | archive-url = https://web.archive.org/web/20100208183720/http://www.hvs.on.ca/modular_jack_wiring.htm | archive-date = 2010-02-08 }}</ref><ref>{{citation | url = http://www.siemon.com/us/standards/13-24_modular_wiring_reference.asp | publisher = Siemon | title = Modular wiring reference}}</ref> and has pins 4 and 5 (the middle positions) wired for the ring and tip conductors of a single telephone line and pins 7 and 8 shorting a programming resistor. This is a different mechanical interface and wiring scheme than ANSI/TIA-568 T568A and T568B schemes with the 8P8C connector in Ethernet and telephone applications. Generic 8P8C modular connectors are similar to those used for the RJ45S variant, although the RJ45S plug is keyed and not compatible with non-keyed 8P8C modular jacks.

Telephone installers who wired RJ45S modem jacks or RJ61X telephone jacks were familiar with the pin assignments of the standard. However, the standard unkeyed modular connectors became ubiquitous for computer networking and informally inherited the name ''RJ45''.

===Standardization===
The shape and dimensions of an 8P8C modular connector are specified for US telephone applications by the Administrative Council for Terminal Attachment (ACTA) in national standard [[ANSI]]/TIA-1096-A and international standard ISO-8877. This standard does not use the short term 8P8C and covers more than just 8P8C modular connectors, but the 8P8C modular connector type is the eight-position connector type described therein, with eight contacts installed.

For [[data communication]] applications ([[LAN]], [[structured cabling]]), International Standard [[IEC]] 60603 specifies in parts 7-1, 7-2, 7-4, 7-5, and 7-7 not only the same physical dimensions but also high-frequency performance requirements for shielded and unshielded versions of this connector for carrying frequencies up to 100, 250 and 600&nbsp;[[MHz]].

===Pinout===
[[File:RJ-45 TIA-568A Left.svg|thumb|T568A wiring, defined in TIA-568]]
[[File:RJ-45 TIA-568B Left.svg|thumb|T568B wiring, defined in TIA-568]]
8P8C connectors are frequently terminated using the T568A or T568B assignments that are defined in ANSI/TIA-568. The drawings to the right show that the copper connections and pairing are the same, the only difference is that the orange and green pairs (colors) are swapped.  A cable wired as T568A at one end and wired as T568B at the other end (Tx and Rx pairs reversed) is an [[Ethernet crossover cable]]. Before the widespread acceptance of [[auto MDI-X]] capabilities, a crossover cable was needed to interconnect similar network equipment (such as [[Ethernet hub]]s to Ethernet hubs). Crossover cables are sometimes still used to connect two computers together without a switch or hub, however, most network interface cards (NIC) in use today implement auto MDI-X to automatically configure themselves based on the type of cable plugged into them. A cable wired the same at both ends is called a [[Patch cable|''patch'' or ''straight-through'' cable]], because no pin/pair assignments are swapped. If a ''patch'' or ''straight'' cable is used to connect two computers with auto MDI-X capable NICs, one NIC will configure itself to swap the functions of its Tx and Rx wire pairs.

{| class="wikitable" style="text-align: center;"
|-
! Pin !! T568A pair !! T568A color !! T568B pair !! T568B color !! 10BASE-T/100BASE-TX signal<ref>IEEE 802.3 ''14.5.1 MDI connectors''</ref> !! 1000BASE-T/10GBASE-T signal !! Wire !! Diagram
|-
| 1 || 3 ||[[File:Wire white green stripe.svg|60px|Pair 3 Tip]]<br />white/green stripe || 2 ||[[File:Wire white orange stripe.svg|60px|Pair 2 Tip]]<br />white/orange stripe|| TD+ || DA+ || tip  
| rowspan=8 width=300px | [[File:Rj45plug-8p8c.png|300px]]
Pin numbering on plug face. Connected pins on plug and jack have the same number.
|-
| 2 || 3 || |[[File:Wire green.svg|60px|Pair 3 Ring]]<br />green solid || 2 ||[[File:Wire orange.svg|60px|Pair 2 Ring]]<br />orange solid|| TD− || DA− || ring 
|-
| 3 || 2 ||[[File:Wire white orange stripe.svg|60px|Pair 2 Tip]]<br />white/orange stripe || 3 ||[[File:Wire white green stripe.svg|60px|Pair 3 Tip]]<br />white/green stripe|| RD+ || DB+ || tip  
|-
| 4 || 1 ||[[File:Wire blue.svg|60px|Pair 1 Ring]]<br />blue solid || 1 ||[[File:Wire blue.svg|60px|Pair 1 Ring]]<br />blue solid|| {{D-Out|not used}} || DC+ || ring 
|-
| 5 || 1 ||[[File:Wire white blue stripe.svg|60px|Pair 1 Tip]]<br />white/blue stripe || 1 ||[[File:Wire white blue stripe.svg|60px|Pair 1 Tip]]<br />white/blue stripe|| {{D-Out|not used}} || DC− || tip  
|-
| 6 || 2 ||[[File:Wire orange.svg|60px|Pair 2 Ring]]<br />orange solid || 3 ||[[File:Wire green.svg|60px|Pair 3 Ring]]<br />green solid|| RD− || DB− || ring 
|-
| 7 || 4 ||[[File:Wire white brown stripe.svg|60px|Pair 4 Tip]]<br />white/brown stripe || 4 ||[[File:Wire white brown stripe.svg|60px|Pair 4 Tip]]<br />white/brown stripe|| {{D-Out|not used}} || DD+ || tip  
|-
| 8 || 4 ||[[File:Wire brown.svg|60px|Pair 4 Ring]]<br />brown solid || 4 ||[[File:Wire brown.svg|60px|Pair 4 Ring]]<br />brown solid|| {{D-Out|not used}} || DD− || ring 
|}

===Types and compatibility===
Two types of 8P8C plugs and [[crimp connection|crimping]] tools for installing the plug onto a cable are commonly available: Western Electric/Stewart Stamping (WE/SS) and Tyco/AMP.  While the two types are similar, the tooling and plug types cannot be interchanged.{{efn|WE/SS and Tyco/AMP 8P8C plugs have different spacings for the cable strain relief.<ref>{{cite web | url = https://belfuse.com/resources/StewartConnector/Stewart%20Data%20Sheets/CT300064.pdf | title = Stewart Connector 937-SP-3088 – Eight conductor/eight position line cord module | access-date = 2018-04-18 | date = 2006-02-01 | publisher = Bel Stewart Connector | location = Glen Rock, Pennsylvania | archive-url = https://web.archive.org/web/20180418230627/https://belfuse.com/resources/StewartConnector/Stewart%20Data%20Sheets/CT300064.pdf | archive-date = 2018-04-18 | url-status = dead }}</ref><ref>{{cite web | url = http://www.tycoelectronics.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Customer+Drawing%7F554739%7FP%7Fpdf%7FEnglish%7FENG_CD_554739_P.pdf | title = Tyco/AMP 5-554739-2 – Modular plug assembly, 8 position, flat oval cable | access-date  = 2009-09-10 | date = 2008-03-31 | publisher = Tyco Electronics | location = [[Harrisburg, Pennsylvania]] | archive-date =  2011-07-24 | archive-url = https://web.archive.org/web/20110724001504/http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Customer+Drawing%7F554739%7FP%7Fpdf%7FEnglish%7FENG_CD_554739_P.pdf | url-status = dead}}</ref>  Using a WE/SS 8P8C crimp die set on a Tyco/AMP 8P8C plug crushes the top of the connector and damages the crimp die set, and vice versa.}}  WE/SS compatible plugs are available from a large number of manufacturers, whereas Tyco/AMP plugs are produced exclusively by [[Tyco Electronics]].{{citation needed|date=February 2019}} Both types of modular plugs can be mated with a standard 8P8C modular jack.

Both types of 8P8C plugs are available in shielded and unshielded varieties for different [[attenuation]] tolerances as needed. Shielded plugs are more expensive and require shielded cable, but have a lower attenuation, and may reduce [[electromagnetic interference]].

Although a narrower 4-pin and 6-pin plug fits into the wider 8-pin jack and makes a connection with the available contacts on the plug, because the body of the smaller connector may stress the remaining contacts,{{efn|The body of a 6P6C or 4P4C plug typically projects out by more than one millimeter further than the contacts and presses the outermost contacts of the larger connector further than if a full-size connector were inserted.}} the smaller connector can potentially damage the springs of the larger jack.

=== Applications ===
8P8C connectors are commonly used in computer networking applications, where interconnecting cables are terminated at each end with an 8P8C modular plug wired according to TIA/EIA standards. Most wired Ethernet communications are carried over Category 5e or Category 6 cable terminated with 8P8C modular plugs. The connector is also used in other telecommunications connections, including ISDN and [[T-carrier|T1]].

Where building network and telephone wiring is pre-installed, the center (blue) pair is often used to carry [[telephony]] signals. While this allows an RJ11 plug to connect, it may damage the modular jack; an approved converter prevents damage. In landline telephony, an 8P8C jack is used at the point a line enters the building to allow the line to be broken to insert automatic dialing equipment, including [[intrusion alarm]] panels.

The [[Electronic Industries Alliance|EIA]]/TIA-561 standard describes the use of 8P8C connectors for RS-232 serial interfaces.<ref>{{Citation | publisher = Zytrax | url = http://www.zytrax.com/tech/layer_1/cables/tech_rs232.htm#rj45 | title = Layer 1 | contribution = RJ45}}.</ref> This application is common as a console interface for [[network equipment]], such as [[Network switch|switches]], [[router (computing)|router]]s, and [[headless computer]]s.

8P8C modular connectors are also commonly used as a microphone connector for [[Professional mobile radio|PMR]], [[Land mobile radio|LMR]], and [[amateur radio]] transceivers.  Frequently the pinout is different, usually mirrored (i.e. what would be pins 1 to 8 in the ANSI/TIA-568 standard might be pins 8 to 1 in the radio and its manual).

In analog mobile telephony, the 8P8C connector was used to connect an [[Advanced Mobile Phone System|AMPS]] cellular handset to its (separate) base unit; this usage is now obsolete.

The physical connector is standardized as the IEC 60603-7 8P8C modular connector with different ''categories'' of performance. The physical dimensions of the male and female connectors are specified in ANSI/TIA-1096-A and ISO-8877 standards and normally wired to the T568A and T568B pinouts specified in the ANSI/TIA-568 standard to be compatible with both telephone and Ethernet.

A similar standard jack once used for modem and data connections, the RJ45S, used a ''keyed'' variety of the 8P8C body with an extra tab that prevents it from mating with other connectors; the visual difference compared to the more common 8P8C is subtle, but it is a different connector. The original RJ45S<ref name="HVS" /><ref>{{cite web |url= http://www.siemon.com/us/standards/13-24_modular_wiring_reference.asp |title= Modular Wiring Reference |publisher= Siemon |access-date = 2010-10-14}}</ref> keyed 8P2C modular connector, obsolete today, had pins 5 and 4 wired for tip and ring of a single telephone line and pins 7 and 8 shorting a programming resistor.

Electronics catalogs commonly advertise 8P8C modular connectors as ''RJ45''.  An installer can wire the jack to any pin-out or use it as part of a generic [[structured cabling]] system such as ISO/IEC 15018 or [[ISO/IEC 11801]] using 8P8C patch panels for both phone and data.

===Crossover cables===
A router-to-router [[crossover cable]] uses two 8-position connectors and a [[unshielded twisted pair]] (UTP) cable with differently wired connectors at each end.

==10P10C==
<!-- [[10P10C]] redirects here. -->
[[File:10P10C-socket pinout.svg|thumb|The pin arrangement for a 10P10C socket]]
[[File:Connector10p10c.jpg|thumb|left|A 10P10C plug]]

The '''10P10C''' connector is commonly referred to as an '''RJ50''' connector,<ref>{{Cite web |date=2023-01-15 |title=RJ50 - Everything you need to know ! |url=https://instrumentic.info/en/connectors/rj50.html#gsc.tab=0 |access-date=2024-08-20 |website=instrumentic.info |language=en-US}}</ref> although this was never a standard registered jack. The 10P10C has 10 contact positions and 10 contacts.

The most common uses of the 10P10C connector are in proprietary data transfer systems.<ref>{{Citation | publisher = Pinouts guide | url = http://pinoutsguide.com/connector/10_pin_RJ50_10P10C_male_connector.shtml | title = 10 pin RJ50 (10P10C) male | type = connector diagram and applications | access-date = 2010-10-17 | archive-url = https://web.archive.org/web/20130518232747/http://pinoutsguide.com/connector/10_pin_RJ50_10P10C_male_connector.shtml | archive-date = 2013-05-18 | url-status = dead }}</ref>

==Standards==
* ANSI/TIA-968-A: {{webarchive |url=https://web.archive.org/web/20180928200316/https://www.part68.org/SecureDocuments/TIA-968-A-Final.pdf |title=Telephone terminal equipment: Technical requirements for connection of terminal equipment to the telephone network}}
* ANSI/TIA-1096-A: Telecommunications telephone terminal equipment connector requirements for connection of terminal equipment to the telephone network
* IEC 60603-7-1: Connectors for electronic equipment: Part 7-1: Detail specification for 8-way, shielded free and fixed connectors with common mating features, with assessed quality
* IEC 60603-7-2: Connectors for electronic equipment: Part 7-2: Detail specification for 8-way, unshielded, free and fixed connectors, for data transmissions with frequencies up to 100&nbsp;MHz
* IEC 60603-7-4: Connectors for electronic equipment: Part 7-4: Detail specification for 8-way, unshielded, free and fixed connectors, for data transmissions with frequencies up to 250&nbsp;MHz
* IEC 60603-7-5: Connectors for electronic equipment: Part 7-5: Detail specification for 8-way, shielded, free and fixed connectors, for data transmissions with frequencies up to 250&nbsp;MHz
* IEC 60603-7-7: Connectors for electronic equipment: Part 7-7: Detail specification for 8-way, shielded, free and fixed connectors, for data transmissions with frequencies up to 600&nbsp;MHz
* ISO/IEC 8877, EN 28877: Information Technology—Telecommunications and Information Exchange between Systems—Interface Connector and Contact Assignments for ISDN Basic Access Interface Located at Reference Points S and T
* US government documents define registered jack applications of modular connectors for telecommunications.{{efn|4P4C and 10P10C connectors are {{em|not}} defined in these standards.}} See {{slink|Registered jack|History and authority}}

==See also==
*[[BS 6312]] – British equivalent to RJ25
*[[EtherCON]] – ruggedized 8P8C Ethernet connector
*[[XJACK]] - retractable 8P8C Ethernet connector 
*[[GG45]]
*[[TERA]]

==Notes==
{{Notelist}}

==References==
{{Reflist}}

==Bibliography==
* {{Citation | last = Trulove | first = James | date = December 19, 2005 | title = LAN wiring | edition = 3rd | publisher = McGraw-Hill Professional | isbn = 0-07-145975-8}}.

== External links ==
{{Commons category|Modular connectors}}
*{{WikiHow|Make-a-Network-Cable|Make a Network Cable}}
*{{webarchive |url=https://web.archive.org/web/20130215152924/http://www.l-com.com/multimedia/catalog_page/lcom_082-06_Premium_Modular_Plugs.pdf |title=Premium Modular Plugs}} Catalog page showing the difference between solid and stranded contacts

{{Audio and video interfaces and connectors}}
{{UTP cables}}
{{Authority control}}

{{DEFAULTSORT:Modular Connector}}
[[Category:Computer connectors]]
[[Category:Ethernet]]
[[Category:Modularity|Connector]]
[[Category:Networking hardware]]
[[Category:Telephone connectors]]