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86 lines
6.5 KiB
Plaintext
86 lines
6.5 KiB
Plaintext
Episode: 2433
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Title: HPR2433: You were right, I was wrong
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Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr2433/hpr2433.mp3
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Transcribed: 2025-10-19 02:54:20
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---
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This in HPR episode 2,433 entitled, you were right, I was wrong, it is hosted by Ken Fallon
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and is about 9 minutes long and Karima Cleanflag, the summer is, can eat humble pie.
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This episode of HPR is brought to you by AnanasThost.com.
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Get 15% discount on all shared hosting with the offer code HPR15, that's HPR15.
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Better web hosting that's honest and fair at AnanasThost.com.
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Hi everybody, my name is Ken Fallon and you are listening to another episode of Hacker
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Public Radio.
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Back in community news for October 2017, HPR2416, I was commenting about Shane Channon's show
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about putting ends on to cast 6 Ethernet cables.
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He was using straight through wiring for EIA, TIA568B standard when wiring up his church.
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I pointed out that this should probably have been crossed over cables, I was 100% wrong
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on this so apologies to him and allow me to set the record straight here, I'm going to
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have text-to-speech readout a small section of the Wikipedia article untwisted pair.
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So let's play that right now.
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History.
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Wire transposition on top of all the earliest telephones used telegraph lines, or open wire single wire
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for return circuits. In the 1800 and 180 electric trams were installed in many cities,
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which induced noise into these circuits.
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lawsuit speaking on a mailing, the telephone company is converted to balanced circuits,
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which had the incidental benefit of reducing attenuation, hence increasing range.
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An electrical power distribution became more commonplace, this measure proved inadequate.
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Two wires, strung on either side on crossbar on utility poles, shared the route with electrical
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power lines. Within a few years, the growing use of electricity again brought an increase
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of interference, so engineers devised a method called wire transposition to cancel out
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interference. In wire transposition, the wire next changed position once every several poles.
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In this way, the two wires would receive similar EMI from power lines.
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This reprimanded an early implementation of twisting, with a twist rate of about four
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twist per kilometer or six per mile. Such open wire balanced lines with periodic transposition
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still survived today in some rural areas. Twisted pair cabling was invented by Alibman
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in 1881. Three by 1900, the entire American telephone line network one either twisted pair,
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or open wire with transposition to guard against interference. Today, most of the millions of
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kilometers of twisted pairs in the world are outdoor and lines owned by telephone companies,
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used for voice service, and only handled or even seen by telephone workers.
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If we go over to actually what the spec says, and this is the from the Wikipedia article
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over twisted pair in the cabling section. Twisted pair Ethernet standards are such
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that the majority of cables can be wired, straight through, bin 1 to bin 1, bin 2 to bin 2,
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and so on, but others may need to be wired in the crossover, form, receive to transmit,
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and transmit to receive. It is conventional to wire cables for 10 or 110 bits,
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such as Ethernet to either T5168A or T5168B standards. Since these standards differ only in
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that case what the position on the two pair used for transmitting, and receiving TX-RX,
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a cable with T5168A wiring at one end, and T5168B wiring at the other is referred to
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as a crossover cable. The term used in the explanation on the 5168 standards,
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tip and ring, refer to older communication technologies, and equate to the positive,
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and negative parts of the connections. A 10-masty, or 100-masty X node, such as a PC use in a
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connector wiring called medium dependent interfaces, MDI, transmitting on bin 1, and 2 and
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receiving on bin 3, and 6 to a network device. An infrastructure node, a hub, or a switch,
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accordingly use in a connector wiring called MDIX, transmitting on bin 3, and 6 and receiving
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on bin 1, and 2. These ports are connected using a straight-through cable, so each transmitter
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talks to the receiver on the other side. Nodes can have two types on ports, MDI,
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Uplink port, or MDIX, Renewal port, X, for internal crossover. Herb and switches have
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Renewal ports. Rooters, servers and end-nodes, for example personal computers, have
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Uplink ports. When two nodes having the same type on ports need to be connected, a crossover
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cable is often required at speeds of 10, or 100 mbit, such as, else connecting nodes having
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different type on ports, i.e., MDI-MDIX, and vice versa, requires straight-through cable,
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thus connecting an end-node to a hub, or switch requires a straight-through cable.
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On switches such hubs sometimes a button is provided to allow a port to act as either a normal,
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regular, or a Uplink port, i.e. using MDIX, or MDI bin out respectively.
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Many modern Ethernet hosts an app, thus can automatically detect another computer connected
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with a straight-through cable, and an automatically introduce the required crossover, if needed,
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if either on the app, thus this capability, and a crossover cable is required.
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Most newer switches have automatic crossover, auto MDIX, or auto Uplink, on all ports,
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eliminating the Uplink port, and the MDI slash MDIX switch, and allowing all connections to be made
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with straight-through cables, if most devices being connected support 1000 based according to the standards,
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they will connect, regardless of whether a straight-through or crossover cable is used.
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I hope that clarifies it for you, and I guess the point I would like to make is that
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are you going to learn from your mistakes? Well, in this case, yes, this is going to be burned
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into my brain forever. Thanks very much Shane for putting on the show. Thanks very much,
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Windigo, for correcting, and here is a song dedicated to both of you guys from the Memphis 5
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entitled, Who's Sorry Now?
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You've been listening to Hecker Public Radio at Hecker Public Radio dot org.
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We are a community podcast network that releases shows every weekday, Monday through Friday.
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Today's show, like all our shows, was contributed by an HPR listener like yourself.
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If you ever thought of recording a podcast, then click on our contributing
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to find out how easy it really is. Hecker Public Radio was founded by the digital
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dog pound and the infonomican computer club, and it's part of the binary revolution at binrev.com.
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If you have comments on today's show, please email the host directly, leave a comment on the website
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or record a follow-up episode yourself. Unless otherwise stated, today's show is released on
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creative comments, attribution, share a life, 3.0 lives in this video.
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