[rescue] doubt regarding wireles ethernet...

Thu Jul 19 09:16:31 CDT 2001

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>hello sir
>my name is narendran..........i am a student of electronics and 
>communication engg from india.
>i am planning to set up a wireless connection between a computer in 
>our microwave lab and a neighbouring network of computers.
>That is i am trying to make a computer look as if it is one of the 
>lan computers.....but linked through wireless....i have an idea in 
>mind......i have a pair of transceivers operating at 434Mhz.
>which can transmit serial digital data......and receive digital data 
>serially......i initially wanted to connect the ethernet o/p port of 
>my standalone computer to the transmitter(TX1) at its o/p. then this 
>transmitter would transmit the data to the receiver(RX2) on the 
>other side.....and the rx's i.e(RX2)'s o/p can be fed as i/p to the 
>ethernet port.....on the other side.....but i have a problem...
>i have found out that in the ethernet cable there are actually 8 
>wires running through...the 10baseT cable......
>among these 2 are called Tx+ and Tx- and 2 are called Rx+ and Rx-.
>that makes 4 of the wires....the remaining wires are unused it 
>seems........(and not marked  for even some purpose as ground).
>by examining the connections between the computer and the device at 
>the other end.....i found out that the the connections through the 
>10BaseT cable were as below between the two RJ45 connectors of the 
>computer and the hub or the other compuer that is on the other 
>side.........
>
>RJ45 pin(my computer)                       RJ45 pin(hub)
>
>pin1 <---------[ TX+ ]-------------------------[ RX+ ]--> pin3
>
>pin2 <---------[ TX- ]--------------------------[ RX- ]--> pin6
>
>pin3 <---------[ RX+ ]-------------------------[ TX+ ]--> pin1
>
>pin6 <---------[ RX- ]--------------------------[ TX- ]--> pin2
>
>but unfortunately i dont know the functions of the Tx+,Rx+,Rx-,Tx- 
>pins........clearly as of yet
>however........ i have a hunch that the digital data is sent through 
>the Tx+ of the computer and received at Rx+ at the other 
>end........can you clarify that point.......?? as to whether what i 
>have in mind is correct...........but i dont know what for the Tx- 
>and Rx- pins are used for.......by the way i have no information as 
>to how the grounds at the two sides are connected......??
>
>like if you want to feed some input from the output of say........an 
>amplifier to the next stage amplifier we always connect the o/p to 
>the i/p of the next stage.......and the grounds together........as 
>it is the reference....but i am not able to find something like 
>this.....
>could you clarify these points......i am sure you people must have 
>come across these points...some time or the other...it would be very 
>very useful to me if you could help me with some information on even 
>one of these points.....as without clearly knowing the use of Tx+
>and Rx+ and Tx- and Rx- i will not be able to know what should be 
>given as i/p to my transmitter and where the receiver's o/p on the 
>other side should be given to......

what you have here is a 20mhz signal.  When an ethernet station 
transmits it sends 1volt peak to peak across the transmit pins.  This 
signal is modulated with Manchester encoding.  This serves as both a 
clock signal and a data signal.  A zero looks like this(---|__), a 
one looks like this(__|---).  So a positive to negative transition 
means 0, and a negative to positive transition means 1.  What you 
need to do is set it up so that the voltage accross pins 1 and 2 on 
your computer gets fed into the amplifier on the transmitter.  The 
reciever should be able to demodulate that signal and supply the same 
voltage accross pins 3 and 6 on the hub.  The same should be done for 
the other(hub back to computer) channel.  I hope this helps.
daniel

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blockquote, dl, ul, ol, li { padding-top: 0 ; padding-bottom: 0 }
 --></style><title>Re: [rescue] doubt regarding wireles
ethernet...</title></head><body>
<blockquote type="cite" cite><font face="Arial" size="+1">hello
sir</font></blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">my name is
narendran..........i am a student of electronics and communication
engg from india.</font></blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">i am
planning to set up a wireless connection between a computer in our
microwave lab and a neighbouring network of
computers.</font></blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">That
is i am trying to make a computer look as if it is one of
the lan computers.....but linked through wireless....i have an idea in
mind......i have a pair of transceivers operating at
434Mhz.</font></blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">which can
transmit serial digital data......and receive digital data
serially......i initially wanted to connect the ethernet o/p port of
my standalone computer to the transmitter(TX1) at its o/p. then
this transmitter would transmit the data to the receiver(RX2) on the
other side.....and the rx's i.e(RX2)'s o/p can be fed as i/p to the
ethernet port.....on the other side.....but i have a
problem...</font></blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">i have found
out that in the ethernet cable there are actually 8 wires running
through...the 10baseT cable......</font></blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">among these
2 are called Tx+ and Tx- and 2 are called Rx+ and
Rx-.</font></blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">that makes 4
of the wires....the remaining wires are unused it seems........(and
not marked  for even some purpose as ground).</font></blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">by examining
the connections between the computer and the device at the other
end.....i found out that the the connections through the 10BaseT cable
were as below between the two RJ45 connectors of the
computer and the hub or the other compuer that is on the other
side.........</font><br>
</blockquote>
<blockquote type="cite" cite><font size="+1">RJ45 pin(my
computer)          <span
></span
>           <span
></span>  RJ45 pin(hub)</font><br>
</blockquote>
<blockquote type="cite" cite><font size="+1">pin1 <---------[ TX+
]-------------------------[ RX+ ]--> pin3</font><br>
</blockquote>
<blockquote type="cite" cite><font size="+1">pin2 <---------[ TX-
]--------------------------[ RX- ]--> pin6</font><br>
</blockquote>
<blockquote type="cite" cite><font size="+1">pin3 <---------[ RX+
]-------------------------[ TX+ ]--> pin1</font><br>
</blockquote>
<blockquote type="cite" cite><font size="+1">pin6 <---------[ RX-
]--------------------------[ TX- ]--> pin2</font><br>
</blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">but
unfortunately i dont know the functions of the Tx+,Rx+,Rx-,Tx-
pins........clearly as of yet</font></blockquote>
<blockquote type="cite" cite><font face="Arial"
size="+1">however........ i have a hunch that the digital data is
sent through the Tx+ of the computer and received at Rx+ at the
other end........can you clarify that point.......?? as to whether
what i have in mind is correct...........but i dont know
what for the Tx- and Rx- pins are used for.......by the way
i have no information as to how the grounds at the two sides are
connected......??</font></blockquote>
<blockquote type="cite" cite> </blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">like if you
want to feed some input from the output of say........an amplifier to
the next stage amplifier we always connect the o/p to the i/p of the
next stage.......and the grounds together........as it is the
reference....but i am not able to find something like
this.....</font></blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">could you
clarify these points......i am sure you people must have come across
these points...some time or the other...it would be very very useful
to me if you could help me with some information on even one of these
points.....as without clearly knowing the use of
Tx+</font></blockquote>
<blockquote type="cite" cite><font face="Arial" size="+1">and Rx+ and
Tx- and Rx- i will not be able to know what should be given as i/p to
my transmitter and where the receiver's o/p on the other side should
be given to......</font></blockquote>
<div><br></div>
<div>what you have here is a 20mhz signal.  When an ethernet
station transmits it sends 1volt peak to peak across the transmit
pins.  This signal is modulated with Manchester encoding. 
This serves as both a clock signal and a data signal.  A zero
looks like this(---|__), a one looks like this(__|---).  So a
positive to negative transition means 0, and a negative to positive
transition means 1.  What you need to do is set it up so that the
voltage accross pins 1 and 2 on your computer gets fed into the
amplifier on the transmitter.  The reciever should be able to
demodulate that signal and supply the same voltage accross pins 3 and
6 on the hub.  The same should be done for the other(hub back to
computer) channel.  I hope this helps. </div>
<div>daniel</div>
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