USOC/568A/568B/258A for POTS wiring
Lindsay Pallickal
going to be a simple operation, to find the standard for POTS wiring
using RJ45 plugs and jacks. If I would ever have to do this again, I
think I'd rather stick a needle in my eye. Or maybe a pitchfork. So
much time to gather so little information, with lots of misinformation
to filter out through cross referencing.
I've tried to document the standards I've come across and put them in
one place for others that might try and do their own phone wiring. I
was careful collecting this data, but I want you guys to review it for
me and let me know if there is something I left out or got wrong. For
each standard I've listed pros and cons, questions, and my judgment
of its worthiness for regular phone wiring. After I get some input
from you guys, I'll post a finalized, more readable, html version
online.
---------------------------------
USOC - RJ61 (an RJ45 plug/jack wired the USOC way)
Assignment Pair Color - UTP Color - Old Style RJ11 RJ12
+--------------- Tip Pair 4 4 White/Brown Brown - -
| +------------- Tip Pair 3 3 White/Green White - 1
| | +----------- Tip Pair 2 2 White/Orange Black - 2
| | | +--------- Ring Pair 1 1 Blue/White Red 1 3
| | | | +------- Tip Pair 1 1 White/Blue Green 2 4
| | | | | +----- Ring Pair 2 2 Orange/White Yellow - 5
| | | | | | +--- Ring Pair 3 3 Green/White Blue - 6
| | | | | | | +- Ring Pair 4 4 Brown/White Orange | | | | | | |
1 2 3 4 5 6 7 8
-------------------
| | | | | | | | | |
| | [ Female RJ45 - Front View ]
| |
|___ ___|
|___ ___|
|_____|
Pros: Backwards compatibility with standard phone system wiring. 2
wire on 2 conductor plug (RJ11), 4 wire on 6 conductor plug (RJ14
wiring on RJ12 plug), and 6 wire on 6 conductor plug (RJ25 wiring on
RJ12 plug), connectors can plug right into a USOC RJ61 jack.
Cons: Plugging RJ11 or RJ12 into RJ61 may mangle the jack's pins some.
Twisted pairs 3 and 4 separate too far from their
partners, allowing radio frequency interference into
those channels. Does this matters for voice? You
can't use USOC wiring for ethernet. I haven't seen
many 3 line and any 4 line phones that plug into this
RJ61 USOC standard, so that would eliminate all of the
pros USOC has over EIA/TIA 568A. Can anyone verify
this?
Questions: Why the heck did they swap ring and tip for pair 2, but
didn't repeat that for pairs 3 and 4? From an
engineer's perspective, what is the benefit of
swapping?
Overall: It stinks, who the heck uses RJ25 and RJ61 phones
anyway. Most phones seem to take 2 x RJ12 for
4 lines.
EIA/TIA 568A
Assignment Pair Color - UTP Color - Old Style
+--------------- Tip Pair 3 3 White/Green White
| +------------- Ring Pair 3 3 Green/White Blue
| | +----------- Tip Pair 2 2 White/Orange Black
| | | +--------- Ring Pair 1 1 Blue/White Red
| | | | +------- Tip Pair 1 1 White/Blue Green
| | | | | +----- Ring Pair 2 2 Orange/White Yellow
| | | | | | +--- Tip Pair 4 4 White/Brown Brown
| | | | | | | +- Ring Pair 4 4 Brown/White Orange
| | | | | | | |
1 2 3 4 5 6 7 8
-------------------
| | | | | | | | | |
| | [ Female RJ45 - Front View ]
| |
|___ ___|
|___ ___|
|_____|
Pros: Backwards compatibility with RJ11 and RJ12 phone plugs. It's
the latest ethernet standard, for full compatibility.
Cons: Only USOC compliant for pairs 1 and 2, so not compatible with 3
line (RJ25) devices or 4 line (RJ61).
Questions: Are there non-networked 3 or 4 line phones that work with
this standard?
Overall: Good compatibility with ethernet for flexibility in wiring,
and again, few use RJ25 and RJ61 anyway.
---------------------------------
EIA/TIA 568B
Assignment Pair Color - UTP Color - Old Style
+--------------- Tip Pair 2 2 White/Orange Black
| +------------- Ring Pair 2 2 Orange/White Yellow
| | +----------- Tip Pair 3 3 White/Green White
| | | +--------- Ring Pair 1 1 Blue/White Red
| | | | +------- Tip Pair 1 1 White/Blue Green
| | | | | +----- Ring Pair 3 3 Green/White Blue
| | | | | | +--- Tip Pair 4 4 White/Brown Brown
| | | | | | | +- Ring Pair 4 4 Brown/White Orange
| | | | | | | |
1 2 3 4 5 6 7 8
-------------------
| | | | | | | | | |
| | [ Female RJ45 - Front View ]
| |
|___ ___|
|___ ___|
|_____|
Pros: Backwards compatibility with RJ11. Works fully with ethernet.
Cons: RJ14 will work, but will yield lines 1 and 3 to a 2 line RJ14
phone as opposed to the standard lines 1 and
2. Only USOC compliant for pair 1, behavior
is atypical for 2 line (RJ14) devices, while
not compatible with 3 line (RJ25) devices or 4
line (RJ61).
Overall: Stick with EIA/TIA 568A, why have the quirk of line 3 popping
up where line 2 is typically expected.
---------------------------------
AT&T 258A
Assignment Pair Color - UTP Color - Old Style
+--------------- Tip Pair 2 2 White/Orange Black
| +------------- Ring Pair 2 2 Orange/White Yellow
| | +----------- Tip Pair 3 3 White/Green White
| | | +--------- Ring Pair 1 1 Blue/White Red
| | | | +------- Tip Pair 1 1 White/Blue Green
| | | | | +----- Ring Pair 3 3 Green/White Blue
| | | | | | +--- Tip Pair 4 4 White/Brown Brown
| | | | | | | +- Ring Pair 4 4 Brown/White Orange
| | | | | | | |
1 2 3 4 5 6 7 8
-------------------
| | | | | | | | | |
| | [ Female RJ45 - Front View ]
| |
|___ ___|
|___ ___|
|_____|
Overall: Identical wiring to EIA/TIA 568B, it is here for clarity.
---------------------------------
Conclusion: Choose EIA/TIA 568A and split to 2 x RJ12 for the endpoint
jacks and the keep the flexibility of using the wiring for ethernet
later.
General Questions: If I wanted to install a networked phone system,
the kind that allows extensions, forwarding calls to other base
stations, and multiple lines, would any of the wiring standards above
offer the most compatibility? I'd really like a response to this one
as I would like to head in this direction eventually.
Are ethernet devices capable of withstanding the high voltages of a
phone line? I have heard that an EIA/TIA 568A wired jack can
be used for phone and ethernet, where the center 2 conductors
carry a single phone line, since those two are only used in
full-duplex communication. It would be important to know this
if installing RJ61 jacks too, since all 8 conductors carry
high voltage and are physically identical to ethernet jacks.
The matching of solid color cable beyond red/green/black/yellow to
ring X and tip X -is that standardized? is my pairing of blue & white
to ring3 & tip3 and orange & brown to ring4 & tip4 correct?
Thanks in advance,
Lindsay