Telephone Cable

Phone cable generally contains two pairs of wires, for two phone lines. The first pair is green and red; the second is black and yellow. The way you remember this is that there are two holidays: Christmas and Halloween. (I apologize if this is a US-centric mnemonic. I encourage everyone around the world to celebrate Halloween.) This set of colors is standardized for stranded wires (where each "wire" consists of about 20 little tiny wires that stick in your fingers and hurt like hell if you aren't careful.) For solid wires, the colors defined below for Ethernet are used; pair 1 is White/Blue+Blue, pair 2 is White/Orange+Orange.

RJ-11 Plug Wiring

This is the wiring for the plug side of an RJ-11 connector. Can you say "BRGY"? (Think about cheap red wine; I know I do.) The diagram is shown with the "hook" - the little thing you press on to get the plug out - underneath. RJ-11 sockets always have the colors indicated on the terminals.

Note that the connector on the other end of an RJ-11 connector is wired in reverse order. That is, if you stretch the cable out flat, the Black wire stays on the left all the way to the other end, including through the connector with the hook oriented down also. Also note that the RJ-11 connector has six terminals on it. Only the middle 4 are normally used. Line 1 is the center pair: red and green, as in Christmas.

T-568A Color Code for RJ-45 Plug

Eight-conductor data cable contains 4 pairs of wires. Each pair consists of a solid (or predominantly) colored wire and a white wire with a stripe of the same color. The pairs are twisted together. To maintain reliability on Ethernet, you should not untwist them any more than necessary (like about 1 cm).

The T568A specification reverses the orange and green connections, so that pairs 1 and 2 are on the center 4 pins, which makes it more compatible with the telco voice connections. (Note that in the RJ-11 plug at the top, pairs 1 and 2 are on the center 4 pins.) T-568A is supposed to be the standard for new installations, while T-568B is an acceptable alternative. However, most off-the-shelf data equipment and cables seem to be wired to T568B. It's important not to mix systems, as both you and your equipment will become hopelessly confused. T568A goes:

  T568B      Used for PHAST Link /   10/100 BaseT / Win 95/98 
    Color Codes for T568A
Pin     color  pair  name
---     -----  ---- ---------
1       wh/grn  3   RecvData+
2       grn     3   RecvData-
3       wh/or   2   TxData +
4       blu     1
5       wh/blu  1
6       or      2   TxData -
7       wh/brn  4
8       brn     4 

And to end the discussion of wire colors, here's a translation table from the RGBY used for two-pair lines to the more colorful combinations used in larger lines:

Eight-conductor data cable contains 4 pairs of wires. Each pair consists of a solid (or predominantly) colored wire and a white wire with a stripe of the same color. The pairs are twisted together. To maintain reliability on Ethernet, you should not untwist them any more than necessary (like about 1 cm).

There are two wiring standards for these cables, called "T-568A" and T-568B" They differ only in connection sequence, not in use of the various colors. The illustration shown is for T-568B. The pairs designated for 10BaseT Ethernet are Orange and Green. The other two pairs, Brown and Blue, can be used for a second Ethernet line or for phone connections.

Note that the Blue pair is on the center pins and conveniently corresponds to the Red and Green pair in a normal phone line. The connections shown are specifically for an RJ45 plug (the thing on the end of the wire). The wall jack may be wired in a different sequence because the wires are actually crossed inside the jack. The jack should either come with a wiring diagram or at least designate pin numbers that you can match up to the color code below.



Pin Number Designations
There are pin number designations for each color in T568A as well. The pin designations are as follows:

   Color Codes for T568B
Pin     color  pair  name
---     -----  ---- ---------
1       wh/or   2   TxData +
2       or      2   TxData -
3       wh/grn  3   RecvData+
4       blu     1
5       wh/blu  1
6       grn     3   RecvData-
7       wh/brn  4
8       brn     4 
Note that the odd pin numbers are always the white with stripe color.
Translation Between Alternative Color Code Systems


1 1 White Blue Green 4
1 2 Blue White Red 3
2 1 White Orange Black 2
2 2 Orange White Yellow 5
3 1 White Green White 1
3 2 Green White Blue 6

Straight-Through vs. Cross-Over
In general, the patch cords that you use with your Ethernet connections are "straight-through", which means that pin 1 of the plug on one end is connected to pin 1 of the plug on the other end. Compare with a telephone cable using RJ-11 plug, as shown at the top of this page. Voice cables are "crossed" end to end; data cables aren't.

The only time you cross connections in 10BaseT is when you connect two Ethernet devices directly together without a hub. Then you need a "cross-over" patch cable, which crosses the transmit and receive pairs, the orange and green pairs in normal wiring. 




What are the pinouts on some AMX cables?

Cable Diagrams
There are several different cables used when programming and operating AMX control systems. The first is the Null Network cable that is used to connect the computer to the PLC-MCU Master Control Unit Card (Landmark). This includes the two industry wiring standards, described as EIA/TIA T568A and EIA/T568B. By doing so, the TX pair will swap places with the RX pair.

Other types of cabling used by AMX Dealers are a Null Modem cable and straight through Serial cables. (DB-9 Female and DB-9 Male shown below.)

The last device on a string of devices should always be terminated using PM-TERM. You can get these terminators from your sales department or, if you have plenty of time on your hands, you can make your own. You will need two 120-Ohm resisters and an RJ-45 plug. The resisters will be connected between pins 1 & 2 and 7 & 8.

Viewpoint Adapter
The adapter cable that is required to program the Viewpoint is another cable that must be used, the adapter consists of a DB-9 Male. This cable is only an adapter you must also use the Null Modem serial cable.

Figure 4   Figure 5
Pin 2 --- R
Pin 3 --- T
Pin 5 --- S


Diagnostic DMS
There is an adapter that will supply power to the Diagnostic DMS. However, you must add jumpers across the communication pairs.

For more details about this and other TechNotes from AMX Tech Support, log onto the AMX Web site. Roll your computer mouse over the user menu (at left) and click on "tech support". At the next screen, roll over 'landmark" and click "faqs". Scroll down the available TechNotes and select "TN12".


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