from:
http://www.aes.org/standards/comments/comments-draft-aes72-xxxx-190215.cfm
Category Archives: T-568A
AES X246 out for comment
AES X246 proposal for standards is out from the SC-02-05 working group.
This give the working group an opportunity to comment on a pattern describing Pair order and caveats of using QTP.
Not letting anything out of the bag because the manufacturers are mixed around.
Something magical about the Quad choice. QTP-4-Everyone
Problems of Assigning Channels Based on Color alone
The need for 8p8c to 8p8c connectivity is of the utmost importance.
Second to is the “field breakouts”. The colour plays a huge part.
I’ve been noticing more and more breakout tails entering the market, so it needs addressing. We cannot use the 25 pair or TIA colour codes to determine the channels.
For the field, I would expect a simple visual inspection to influence deployment decisions. Looking at the solid colours to determine the channel order. Below is an image that has been the result of many conversations. An observation I’d like to present: If you look at RJ45 connectors the solid colours are visible. The order of the solid colour should dictate the channel order. Pair three in both cases is split around pair 2. Pins of multiples of 2 are considered “Hot”. QTP-B is based on the TIA-B wiring scheme. 
This is where a lot of QTP development started. How to terminate this twisted 3M ribbon cable to an RJ45 Jack. Since it would not fit and CAT cable is everywhere…
QTP-A and QTP-B
QTP-A and QTP-B
Making a QTP patching system using DB25 patchbays
Dual row, 24 Channel by 24 Channel
DB25 to DB25 patchbay wiring price:
(12) QTP-DB25M $12.04 = $144.48
(24) CAT6-10-Green $7.80 = $187.20
6 cable price: $331.58
Checking the spacing fit for QTP-DB25M adapters.
Not a single problem detected. With all signals balanced and power on two different phases, no measurable induced noise detected.
Ask us about Bit-Tree patchbays
QTP DB25 Pin out standards
I had an integrator call today asking what the compatible pin outs of the QTP-DB25 adapters were .
QTP-DB25M and QTP-DB25M use the Tascam DB25 Pinout.
Channels 1-4 terminate to one RJ45 and 5-8 to the other.
If you are using AES in and out the pin out is identical.
CH 1-4 are IN 1-4 and CH 5-8 are OUTPUT 5-8 
The Third Compatible pin out is the Yamaha AES pin out. The QTP-DB25Y is only available in a male DB25 connector. The IN the first RJ45 and OUT the second.
All the RJ 45 connectors terminate to the TIA -B standard and use the following pair and polarity designation
QTP-DB25M and QTP-25F
