09-28-2012 07:08 PM - edited 03-07-2019 09:10 AM
Hi everybody.
We connect router say to a computer using a cross over cable, router uses pins 1,2 to transmit and pins 3,6 to receive.
My question is why do we need two pins to transmit? Can we not use just one pin to transmit say pin 1?
What is the benefit of using two pins i.e pin 1 and pin 2 to transmit data?
thanks and have a great weekend.
Solved! Go to Solution.
09-28-2012 07:53 PM
Hi Sarah,
That is based on 568A standard cabling. You need a pair for example for transmit, one is white/green with BI_DI+ and one is green with BI_DI-
See this link for more detail:
http://www.ertyu.org/steven_nikkel/ethernetcables.html
HTH
09-28-2012 07:59 PM
Hello Sarah,
(abbreviation: Tx and Rx) is the process of sending and propagating an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium,
1- The sending of a signal from the transmitting end of a telecommunication circuit to inform a user at the receiving end that a message is to be sent.
2-A data transmission circuit may transfer information in (a) one direction only, (b) either direction but one way at a time, or (c) both directions simultaneously
These are the wiring standards T568A and T568B
http://en.wikipedia.org/wiki/Medium_dependent_interface
hope this will help.
thanks
09-29-2012 07:04 AM
Hello Sarah,
>> What is the benefit of using two pins i.e pin 1 and pin 2 to transmit data?
From an electrical point of view the use of two pins is a form of balanced transmission the information in the signal is coded as the difference in voltage between the two pins
The alternative to this would be an unbalanced setup with a single common ground pin for all transmission pairs.
The benefits of balanced transmission are better resistance to noise and specially less vulnerable to cross talk between different pairs either carrying a signal in opposite direction or in the same direction of the given pair.
Being the actual signal associated to the difference all forms of noise that influence both wires are minimized ( common mode noise rejection)
Reduction of cross talk is the reason behind the twisting of pairs in an UTP cable
Unshielded Twisted Pair
unshielded means that the external cover of the cable is not connected to ground.
see
http://en.wikipedia.org/wiki/Balanced_line
Hope to help
Giuseppe
09-29-2012 11:17 AM
Hi Sarah,
Usually, you use 2 pairs (4 conductors) for 100Mb Ethernet and 4 pairs (all 8 conductors) for Gigabit Ethernet and 10Gig.
Have a nice weekend
Reza
09-29-2012 11:41 AM
Hello Sarah,
>> The use of two balanced lines is one of the reasons why we are able to acheive 1000bits/sec . Is it correct?
yes, the bit stream is divided in two substreams that are sent in parallel on the different transmission pairs.
To be noted the actual speed on the line is greater then 1Gbps because the bit stream is encoded with some overhead to provide error detection and correction.
The actual speed on the wire is 1250 Mbps but the code used is 8 bits of data mapped in 10 bits sent on wire.
see
http://en.wikipedia.org/wiki/Gigabit_Ethernet
Hope to help
Giuseppe
09-28-2012 07:53 PM
Hi Sarah,
That is based on 568A standard cabling. You need a pair for example for transmit, one is white/green with BI_DI+ and one is green with BI_DI-
See this link for more detail:
http://www.ertyu.org/steven_nikkel/ethernetcables.html
HTH
09-29-2012 06:22 AM
Hi Reza and Singh
I hope you guys are doing fine.
The links you did not address the question asto why we need two pins such as pin 1 and pin2 on a router to tranmit data. What are the benifits using two pins insted of one for tranmission.?
Thanks and have a great weekend
09-29-2012 01:14 PM
hello Sarah,
i am doing good, thanks .
It was cat 3 cable with 2 pairs only because its bandwidth was 16 MHz (16 million bits per second). Unsuitable for speeds above 16 Mbit/s. Now mainly for telephone cable.early 2000s most new structured cable installations are built with Cat 5e (100 million bits per second) which achieves speeds of 100 Mbit/s by using all 4 pairs of wires. So to achieve this higer speed bandwidth we need 2 pair to transmit and 2 to receive. 3rd pair used for POE and 5th for gig transfer.
Hope this will help.
thanks
09-28-2012 07:59 PM
Hello Sarah,
(abbreviation: Tx and Rx) is the process of sending and propagating an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium,
1- The sending of a signal from the transmitting end of a telecommunication circuit to inform a user at the receiving end that a message is to be sent.
2-A data transmission circuit may transfer information in (a) one direction only, (b) either direction but one way at a time, or (c) both directions simultaneously
These are the wiring standards T568A and T568B
http://en.wikipedia.org/wiki/Medium_dependent_interface
hope this will help.
thanks
09-29-2012 07:04 AM
Hello Sarah,
>> What is the benefit of using two pins i.e pin 1 and pin 2 to transmit data?
From an electrical point of view the use of two pins is a form of balanced transmission the information in the signal is coded as the difference in voltage between the two pins
The alternative to this would be an unbalanced setup with a single common ground pin for all transmission pairs.
The benefits of balanced transmission are better resistance to noise and specially less vulnerable to cross talk between different pairs either carrying a signal in opposite direction or in the same direction of the given pair.
Being the actual signal associated to the difference all forms of noise that influence both wires are minimized ( common mode noise rejection)
Reduction of cross talk is the reason behind the twisting of pairs in an UTP cable
Unshielded Twisted Pair
unshielded means that the external cover of the cable is not connected to ground.
see
http://en.wikipedia.org/wiki/Balanced_line
Hope to help
Giuseppe
09-29-2012 10:12 AM
Thanks Giuseppe for the detailed response
The use of balanced line reduces noise while twisting reduces cross talk.
Balanced line consists of two conductors.
In case of gigabit ethernet, we use four pins or two pairs to transmit.
So in case of gigabit ethernet, we use two balanced lines to transmit data. The use of two balanced lines is one of the reasons why we are able to acheive 1000bits/sec . Is it correct?
Have a great weekend.
09-29-2012 11:17 AM
Hi Sarah,
Usually, you use 2 pairs (4 conductors) for 100Mb Ethernet and 4 pairs (all 8 conductors) for Gigabit Ethernet and 10Gig.
Have a nice weekend
Reza
09-29-2012 11:41 AM
Hello Sarah,
>> The use of two balanced lines is one of the reasons why we are able to acheive 1000bits/sec . Is it correct?
yes, the bit stream is divided in two substreams that are sent in parallel on the different transmission pairs.
To be noted the actual speed on the line is greater then 1Gbps because the bit stream is encoded with some overhead to provide error detection and correction.
The actual speed on the wire is 1250 Mbps but the code used is 8 bits of data mapped in 10 bits sent on wire.
see
http://en.wikipedia.org/wiki/Gigabit_Ethernet
Hope to help
Giuseppe
09-29-2012 01:49 PM
Thanks Giuseppe.
11-27-2012 11:02 PM
Hi all,
Further to your discussions above, and just to clear this up....
If I am a PC I am using pins 1 & 2 to transmit to a switch, and am using pins 3 & 6 to receive from a switch.
If we had a bit stream of 000111000011110000111100000111 are the 1's transmitted on pin 1 and the 0's on pin 2?
And for receive pin 3 is used to receive 1's and pin 6 used to receive 0's from a switch?
And for a switch, a switch sends 1's on pin 3 and 0's on pin 6 and receives 1'son pin 1 and 0's on pin 2?
I am just trying to clear this up. I've gone through a few docs but am struggling with this concept somewhat!!! Silly I know as this is the basics, but I want to strip this right back to get a better understanding.
Sorry for hijacking the thread!
Cheers,
D
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