Page 4 of 5 FirstFirst ... 2345 LastLast
Results 31 to 40 of 44

Thread: Cat 6 termination, A or B?

  1. #31
    octavian is offline Inactive, Email Never Verified
    Join Date
    Jun 2011
    Posts
    5

    Maybe not a big deal here

    The 568B standard is still more common in the US but I believe slowly moving toward 568A. For what it's worth in DOD work the rule is use A unless B is widely used at the present location. So with no other info use A.

  2. #32
    Join Date
    Mar 2007
    Location
    Valdosta, GA
    Posts
    4,046
    Quote Originally Posted by hbiss View Post
    That is the absolute truth, I've been preaching that for a long time. I've been putting plugs on cables for probably 20 years so you would think I would have it down by now. But I still have to cut some off and re-do them not to mention trying to figure out which end is at fault.

    -Hal
    It's especially difficult when you're color blind



    Sent from my iPhone using Tapatalk
    Brought to you by Carl's Jr.

  3. #33
    Join Date
    Oct 2007
    Location
    New Jersey
    Posts
    5,846
    Quote Originally Posted by brantmacga View Post
    It's especially difficult when you're color blind



    Sent from my iPhone using Tapatalk
    Well, another career choice for my sons to avoid.

  4. #34
    Join Date
    Mar 2018
    Location
    Spokane, Washington, USA
    Posts
    4

    My Twisted Opinion

    I'm new here; pardon me for just "jumping in"; however, I've been dealing with "data cabling" since before "AppleTalk" first started exploring twisted pair usage -- and "Ethernet" referred to some sort of "coax installation for your DEC computer."

    Here are several of points that I did not see completely clarified:
    _
    1. Yes, the "twist rate" will be different between different pairs within the same cable and, it will generally vary between types of cable from the same manufacturer and between different cable manufacturers. The purpose of having a variable twist rate is to keep the cables from "nesting" inside of the overall cable housing. (Think of the way two threaded rod with the same "tread pitch" will "lock together" in their package.) When they nest together, you get increased cross talk. I have dealt with cable manufacturers who had dividers to keep the pairs separate and with manufacturers who used a left-hand twist on two pair, and a right-hand-twist on the other two pair -- making it necessary to have only two twist ratios instead of four.
    _
    While "twist is good" is a rule of thumb, it comes at a cost. The higher the twist rate, the shorter the distance covered by the same amount of wire (I've seen deltas of up to three feet in a 100 meter run). The higher the twist rate, the harder it becomes to terminate the cable -- whether using plugs or jacks (I've crimped thousands of plugs on to Cat 6 Cable, when doing it regularly my failure rate was 0.5%) -- you have to test with a high-quality tester every time.
    There is no sure and certain guarantee that the "green pair" or the "orange pair" or any of the other pairs will be the "best" pair. In fact, at one point, Avaya claimed the "Blue Pair" was the "best pair" in their cables.
    _
    _
    2. The twist rate not only affects how much the cable pairs nest and how much they cross-talk, it also affects the cable's immunity to environmental noise. All things being equal, the higher the twist rate, the more noise immunity you tend to get. Thus, I have seen some devices on some cable that would work on one set of cable pairs, but not on another. Now this was in a situation where we were pressing some first-generation "Level 3" (remember, they called it "Level 3" before there was a "Category 3" designation?) cable that was being used for a 100 meg connection. So, we were "at the margin" to say the least -- technically, it should NOT have worked at all. But, in order to achieve functionality, we rotated the "Blue Pair" (see above) into use along side of the "Green Pair" to get 100mbps with an acceptable (but still non-zero) error rate.
    _
    _
    3. But ALL of this begs the question of the difference between 568A and 568B relative to your camera installation. As has been stated before, in 568A places the "green pair" on pin numbers 1 & 2 while the "orange pair" goes to pin 3 & pin 6. By contrast, 568B puts the "orange pair" on pins 1 & 2 and lands the "green pair" on pins 3 & pin 6. The fact I did not see anyone raise (I apologize if I missed a comment), is that pins 1 & 2 and pins 3 & 6 are ALL part of the SAME bidirectional communications channel.
    _
    From the DTE (Data-communications Terminating Equipment) perspective, pin one is essentially Tx+ pin 2 is Tx- pin 3 is Rx+ and Rx- lands on pin 6. What is "transmit" to one device is "receive" to the other -- which is why you may see the pins designated as "BI_DA+" and "BI_DA-" and "BI_DB+" and "BI_DB-" respectively. So, basically, you are not "improving" the channel by switching the pairs within the channel. You are simply changing which end is "driving" which pair. Assuming both pair meet specs, there should be no problem. If they do not meet specs, it's not like you were swapping a pair that was not part of the link into the connection. Let's say say NEXT (Near End X-Talk) is too high and the camera "hears itself" thereby causing phantom collisions. The inductive and/or capacitive coupling that is causing your issues is bidirectional -- if the green pair "hears" transmissions made on the orange pair, the orange pair will "hear" transmissions made on the green pair and the camera will still fail to transmit -- regardless of which pair it drives and which pair is driven by the other end.



    Oh, and one final point, the whole reason for specifying 568A as opposed to 568B has to do with backwards compatibility, not quality of operation.

    The 568B option matches the old "Ma Bell" 258A color code (can anyone say, "WICO"?) and only matches single (one) pair USOC wiring schemes. Since the Ma Bell or AT&T (Alotta Time & Trouble) spec wiring was far and away the most common in private homes and private companies. This is because, at one time, the "phone company" had to do the wiring, or you would not get service from them. That restriction is why we occasionally had phone jacks screwed to desks -- wanna move your desk? gotta call the phone company! The 568B wiring pattern tends to flow "naturally" in those places.

    Meanwhile, 568A provides "backwards compatibility" with two pair USOC -- which is why the Federal Government generally specifies 568A.

    My $0.02 Worth
    (and that's inflation)

  5. #35
    Join Date
    May 2005
    Location
    Richmond, Virginia
    Posts
    23,004
    Sesq, welcome to the forum. Here, we prefer to eschew obfuscation. Interesting to resurrect a seven-month-old thread, but refreshing to see someone else who understands twisted-pair theory, too. I have run and terminated plenty of UTP cable, and installed camera systems, too.

    One more thing about twist rate: the greater the twists-per-inch, the higher the frequency (i.e., the shorter the wavelength) of interference that the receiver's differential amp can ignore (due to common-mode noise rejection) because the twists assure that both conductors pick up the interfering signal equally.

    Yes, I'm primarily an electrician, but I've been interested in electronics and electrical theory since I was a kid. I built crystal radios when I was 6 (I'm 62 now), installed 8-track stereos when I was a teenager, modified audio equipment, and I am into A/V and home theater now. I remember token-ring networks using coax, too.

    I read Popular Electronics magazine, and built stereo equipment from kits such as Dynaco and SWTPC, and read about, but never built, computers using the 6800 processor. i know more about hardware than software when it comes to computers. I prefer soldering irons and hand and power tools to keyboards.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  6. #36
    Join Date
    Mar 2003
    Location
    New York
    Posts
    1,036
    Rewired an elementary school years ago with cat 5, I'm talking to the Verizon guy punching down the pot head, when a teacher stops and said how nice it will be to have high speed internet so they can access the university library miles away. She walked off and we both burst out laughing.
    What was the name of the shunted term blocks, supposed to have their tool to term with?

  7. #37
    Join Date
    Mar 2003
    Location
    New York
    Posts
    1,036
    Quote Originally Posted by LarryFine View Post
    Sesq, welcome to the forum. Here, we prefer to eschew obfuscation. Interesting to resurrect a seven-month-old thread, but refreshing to see someone else who understands twisted-pair theory, too. I have run and terminated plenty of UTP cable, and installed camera systems, too.

    One more thing about twist rate: the greater the twists-per-inch, the higher the frequency (i.e., the shorter the wavelength) of interference that the receiver's differential amp can ignore (due to common-mode noise rejection) because the twists assure that both conductors pick up the interfering signal equally.

    Yes, I'm primarily an electrician, but I've been interested in electronics and electrical theory since I was a kid. I built crystal radios when I was 6 (I'm 62 now), installed 8-track stereos when I was a teenager, modified audio equipment, and I am into A/V and home theater now. I remember token-ring networks using coax, too.

    I read Popular Electronics magazine, and built stereo equipment from kits such as Dynaco and SWTPC, and read about, but never built, computers using the 6800 processor. i know more about hardware than software when it comes to computers. I prefer soldering irons and hand and power tools to keyboards.
    Larry, I've got a Dynaco amp ~20-30w hit by lightning I need to rebuild one day; Knight kit, Lafayette Radio, like you I can build but never learned coding. Have a raspberry Pi trying to make security/pir/email/photo upload camera but don't know Python. )

  8. #38
    Join Date
    Jul 2006
    Location
    Roughly 5346 miles from Earls Court
    Posts
    2,602
    Quote Originally Posted by sameguy View Post
    Have a raspberry Pi trying to make security/pir/email/photo upload camera but don't know Python. )
    You're lucky, I know enough python to rather despise it (a blot on the landscape of computer languages); AFAICT the only reason it ever got any traction was being new and not Perl.

  9. #39
    Join Date
    Jun 2003
    Location
    Hawthorne, New York NEC: 2014
    Posts
    3,656
    Quote Originally Posted by sameguy View Post
    Rewired an elementary school years ago with cat 5, I'm talking to the Verizon guy punching down the pot head, when a teacher stops and said how nice it will be to have high speed internet so they can access the university library miles away. She walked off and we both burst out laughing.
    What was the name of the shunted term blocks, supposed to have their tool to term with?
    Krone perhaps? Love them for demarcs.

    -Hal

  10. #40
    Join Date
    Mar 2003
    Location
    New York
    Posts
    1,036
    Quote Originally Posted by hbiss View Post
    Krone perhaps? Love them for demarcs.

    -Hal
    Yes.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •