Episode: 2433
Title: HPR2433: You were right, I was wrong
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr2433/hpr2433.mp3
Transcribed: 2025-10-19 02:54:20

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