Editing Registered jack (section)

==RJ21==
{| style="float: right;"
| style="vertical-align: text-top;" | [[File:RJ21-female-connector.jpg|left|80px|thumb|Female RJ21 connector. Pin assignment is coordinated with the table.]] ||
{| class="wikitable" style="float: right; margin-left: 1.5em; margin-right: 0; margin-top: 0;"
|+ Even-count color code
! Color
! Pin<br/>(tip)
!
! Pin<br/>(ring)
! Color
|-
| [[File:Wire white blue stripe.svg|37px]] White/blue
| 26
|
| 1
| [[File:Wire blue white stripe.svg|37px]] Blue/white
|-
| [[File:Wire white orange stripe.svg|37px]] White/orange
| 27
|
| 2
| [[File:Wire orange white stripe.svg|37px]] Orange/white
|-
| [[File:Wire white green stripe.svg|37px]] White/green
| 28
|
| 3
| [[File:Wire green white stripe.svg|37px]] Green/white
|-
| [[File:Wire white brown stripe.svg|37px]] White/brown
| 29
|
| 4
| [[File:Wire brown white stripe.svg|37px]] Brown/white
|-
| [[File:Wire white gray stripe.svg|37px]] White/slate
| 30
|
| 5
| [[File:Wire gray white stripe.svg|37px]] Slate/white
|-
| [[File:Wire red blue stripe.svg|37px]] Red/blue
| 31
|
| 6
| [[File:Wire blue red stripe.svg|37px]] Blue/red
|-
| [[File:Wire red orange stripe.svg|37px]] Red/orange
| 32
|
| 7
| [[File:Wire orange red stripe.svg|37px]] Orange/red
|-
| [[File:Wire red green stripe.svg|37px]] Red/green
| 33
|
| 8
| [[File:Wire green red stripe.svg|37px]] Green/red
|-
| [[File:Wire red brown stripe.svg|37px]] Red/brown
| 34
|
| 9
| [[File:Wire brown red stripe.svg|37px]] Brown/red
|-
| [[File:Wire red gray stripe.svg|37px]] Red/slate
| 35
|
| 10
| [[File:Wire gray red stripe.svg|37px]] Slate/red
|-
| [[File:Wire black blue stripe.svg|37px]] Black/blue
| 36
|
| 11
| [[File:Wire blue black stripe.svg|37px]] Blue/black
|-
| [[File:Wire black orange stripe.svg|37px]] Black/orange
| 37
|
| 12
| [[File:Wire orange black stripe.svg|37px]] Orange/black
|-
| [[File:Wire black green stripe.svg|37px]] Black/green
| 38
|
| 13
| [[File:Wire green black stripe.svg|37px]] Green/black
|-
| [[File:Wire black brown stripe.svg|37px]] Black/brown
| 39
|
| 14
| [[File:Wire brown black stripe.svg|37px]] Brown/black
|-
| [[File:Wire black gray stripe.svg|37px]] Black/slate
| 40
|
| 15
| [[File:Wire gray black stripe.svg|37px]] Slate/black
|-
| [[File:Wire yellow blue stripe.svg|37px]] Yellow/blue
| 41
|
| 16
| [[File:Wire blue yellow stripe.svg|37px]] Blue/yellow
|-
| [[File:Wire yellow orange stripe.svg|37px]] Yellow/orange
| 42
|
| 17
| [[File:Wire orange yellow stripe.svg|37px]] Orange/yellow
|-
| [[File:Wire yellow green stripe.svg|37px]] Yellow/green
| 43
|
| 18
| [[File:Wire green yellow stripe.svg|37px]] Green/yellow
|-
| [[File:Wire yellow brown stripe.svg|37px]] Yellow/brown
| 44
|
| 19
| [[File:Wire brown yellow stripe.svg|37px]] Brown/yellow
|-
| [[File:Wire yellow gray stripe.svg|37px]] Yellow/slate
| 45
|
| 20
| [[File:Wire gray yellow stripe.svg|37px]] Slate/yellow
|-
| [[File:Wire violet blue stripe.svg|37px]] Violet/blue
| 46
|
| 21
| [[File:Wire blue violet stripe.svg|37px]] Blue/violet
|-
| [[File:Wire violet orange stripe.svg|37px]] Violet/orange
| 47
|
| 22
| [[File:Wire orange violet stripe.svg|37px]] Orange/violet
|-
| [[File:Wire violet green stripe.svg|37px]] Violet/green
| 48
|
| 23
| [[File:Wire green violet stripe.svg|37px]] Green/violet
|-
| [[File:Wire violet brown stripe.svg|37px]] Violet/brown
| 49
|
| 24
| [[File:Wire brown violet stripe.svg|37px]] Brown/violet
|-
| [[File:Wire violet gray stripe.svg|37px]] Violet/slate
| 50
|
| 25
| [[File:Wire gray violet stripe.svg|37px]] Slate/violet
|}
|-
|}

RJ21 is a registered jack [[Standardization|standard]] using a [[micro ribbon connector]] with contacts for up to fifty [[Conductor (material)|conductors]]. It is used to implement [[Telecommunication connection|connections]] for up to 25 [[telephone line|lines]], or circuits that require many wire pairs, such as used in the [[1A2 Key System|1A2 key telephone system]]. The [[miniature ribbon connector]] of this interface is also known as a 50-pin telco connector, CHAMP(AMP), or ''Amphenol'' connector, the last being a [[genericized trademark]], as [[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:<ref>{{cite book |last=Ogletree |first=Terry William |title=Upgrading and Repairing Networks |chapter-url=https://books.google.com/books?id=ZHXeT01OSXcC&pg=PA84 |date=2004 |edition=4 |publisher=Que Publishing |isbn=0-7897-2817-6 |page=84 |chapter=Cables, Connectors, Concentrators, and Other Network Components |url-status=live |archive-url=https://web.archive.org/web/20140626201456/http://books.google.com/books?id=ZHXeT01OSXcC&pg=PA84 |archive-date=2014-06-26 }}</ref> 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 50-pin ribbon connectors are often used on [[punch block]]s to create a [[breakout box]] for [[private branch exchange]] (PBX) and other [[key telephone system]]s.
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