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Registered jacks/modular connectors

and their pin outs

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The telephony industry uses dozens of different modular connectors to support different systems.

These modular connectors are referred to as RJ’s (Registered Jack)

We’re going to start with the three most commonly used connectors in telephony

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The three most common registered jacks used for connecting phones and phone equipment are:

RJ-11 RJ-14 RJ-25

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You should know the 4 conductor POTS color code now, this color code is part of the 8 conductor USOC (Universal Service Order Code) color code established by AT&T.

GREEN RED PAIR 1BLACK YELLOW PAIR 2ORANGE BROWN PAIR 3BLUE WHITE PAIR 4

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When looking at the many different RJ style connectors you will notice another code associated with them.For instance:

RJ-11 is a 2P2C (2 position 2 conductor)

RJ-14 is a 4P4C (4 position 4 conductor)

RJ-25 is a 6P6C (6 position 6 conductor) *RJ-61 is a 8P8C (8 position 8 conductor)

*Not a commonly used jack in telephony anymore

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The RJ letter/number designation is followed by and additional letter code.

This letter code provides an indication of the specific application, for instance RJ-11C, the C indicates it’s a flush mount.

The letter code is rarely used in the field, it is a convention used for ordering the correct connectors for specific applications in the field.

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Below is the letter code designations:

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

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Lets compare the different RJs and color codes in more detail.

RJ-11C with the standard color code

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RJ-14C with the standard color

code

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RJ-25C with the standard color code

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RJ-61X with the standard color code

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This diagram is the AT&T network standard that matches the TIA/EIA 568B, RJ-45 standard.We will look at RJ-45s when we get into networks.

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You should notice that the 1st pair GREEN/RED OR WHITE/BLUE-BLUE/WHITE always lines up in the middle of all of the USOC RJs.

The middle position in the RJ series is where the dial tone will always be located on both the plugs and jacks.

Remember that pin assignments change but pair colors never change, don’t confuse pin colors with pair colors.

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Now we will take a closer look at the two color standards and how they match up.

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Here is an example of a CAT 3 4 pair cable being terminated on an old POTS interface

Does this look like it is wired correctly, notice the tip and ring polarity?

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The USOC color code is rarely used unless your terminating CAT 3 devices.

Some CAT 3 connectors and jacks utilize an IDC (Insulation Displacement Contact) type of termination

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IDC JACKS

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IDC jacks require a punch tool to terminate cables onto them which is normally a 110 style punch down.

All IDC components will have the category listing on them.

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You will find that the majority of residential dwellings and small businesses will still have jacks that use the USOC color code.

All telephone line cords still utilize the USOC color code.

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Another RJ that you will need to be familiar with is a RJ-21X.

The RJ-21X is found in business applications and establishes the D-MARC.

The RJ-21X is a 50 pin (25 pair) 66 block that provides up to 25 POTS lines

It is identified by an orange cover, the inside of the cover will list the phone numbers provide by the public utility

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RJ-21X:

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The RJ-21X below doesn’t have the orange cover on it but it shows the specific type of 66 block that it is.

On one side of the block is a 50 pin Amphenol interface typical of all RJ-21Xs, to it’s right is the Amphenol plug

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From the RJ-21X we extend the POTS line to any location within a building.

A POTS line may need to be extended to a burglar alarm panel onto a RJ-31X (alarm panel jack) or into a fire alarm panel or into a PBX (Private Branch Exchange)

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Below we see the RJ-31X kit, then the opened jack and finally the installation in an alarm panel. This will be discussed in further detail in the intrusion alarm course.

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It is possible that in your travels you may come across an old 4 prong jack from the “50s & 60s”.

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In this case you can either use a 4 prong adapter that converts to a RJ interface or cut the jack and wire in a new CAT 3 jack or make a new RJ-14C plug for the phone’s line cord.

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4 prong adapters

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The last thing we’re going to discuss today is the 25 pair color code, you already know the 4 pair color code we will expand on that knowledge.

This color code is the basis for all we do in the tele-data communications industry.

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The 25 pair color code is a 5 X 5 matrix

The 5 tip colors are:WHITE RED BLACK YELLOW VIOLET

The 5 ring colors are:BLUE ORANGE GREEN BROWN SLATE

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SEE THE 25 PAIR COLOR CODE HANDOUT

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