This is why I love this list. Lawrence, you are the "Dude of the day".
In my home we shall honor you this evening as we dine and argue about my uselessness. Useless yes, but now I posses knowledge that they do not and that, my friend - thanks to you - will make all the difference. My hat is off to you. If I wore one, that is....... Bob- -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Lawrence E. Bakst Sent: Thursday, March 11, 2010 3:38 PM To: WISPA General List Subject: Re: [WISPA] Ethernet LEDs The link LED and all other LEDs for Ethernet Jacks/Connections are driven by the Ethernet PHY chip or the Ethernet chip itself the PHY is integrated. Link is turned on by the PHY sensing the LIT (link integrity test) in 10BaseT which I believe has become part of the auto-negotiation protocol in later standards. This is part of the Layer-1 (Physical Later) protocol in the spec. http://en.wikipedia.org/wiki/Autonegotiation So to be clear it's not just a LED hooked up to one of the wire via a resister or some analog hack like that. The PHY knows that their is another PHY on the other side of the cable and if the PHY sees the other PHY it turns on the LINK light. PHYs often provide other lines to show collision, speed, and duplex and these can be tied into other individual LEDS or bi-color LEDs. If the link lights are on at both ends the connection is good. It still might be the case that a duplex mismatch or bad auto-speed negotiation could cause problems. Both of these problems show up from time to time, especially on older gear. For both cases the cure is often to fix the speed or duplex on one side and that prevents the auto-negotiation from failing. One cause of not getting a link light is that a MDI/MDI-X mismatch. Most newer chips have auto MDI/MDI-X which prevents the problem in most cases. leb At 12:52 PM -0500 3/11/10, Robert West wrote: >Yeah, but which circuit? The transmit, receive or maybe the unused pairs? > >That got me wondering also. > >Anyone know what pair triggers the light??? > >Bob- > > >-----Original Message----- >From: [email protected] [mailto:[email protected]] On >Behalf Of Justin Wilson >Sent: Thursday, March 11, 2010 12:15 PM >To: WISPA General List >Subject: Re: [WISPA] Ethernet LEDs > >Simple terms it's the completion of a circuit. > >--- >Justin Wilson <[email protected]> > >On Mar 11, 2010, at 11:29 AM, Cameron Crum <[email protected]> wrote: > >> This may be a little out there, but does anyone know what causes the >> "link" light to show on an ethernet jack when the cable is plugged in? >> Is it as simple as just attaching an led to one of the signal wires, >> or >> is there some logic in there. Just curious. >> >> >> --- >> --- >> --- >> --- >> -------------------------------------------------------------------- >> WISPA Wants You! Join today! >> http://signup.wispa.org/ >> --- >> --- >> --- >> --- >> -------------------------------------------------------------------- >> >> WISPA Wireless List: [email protected] >> >> Subscribe/Unsubscribe: >> http://lists.wispa.org/mailman/listinfo/wireless >> >> Archives: http://lists.wispa.org/pipermail/wireless/ > > >--------------------------------------------------------------------------- - >---- >WISPA Wants You! Join today! >http://signup.wispa.org/ >--------------------------------------------------------------------------- - >---- > >WISPA Wireless List: [email protected] > >Subscribe/Unsubscribe: >http://lists.wispa.org/mailman/listinfo/wireless > >Archives: http://lists.wispa.org/pipermail/wireless/ > > > >--------------------------------------------------------------------------- ----- >WISPA Wants You! Join today! >http://signup.wispa.org/ >--------------------------------------------------------------------------- ----- > >WISPA Wireless List: [email protected] > >Subscribe/Unsubscribe: >http://lists.wispa.org/mailman/listinfo/wireless > >Archives: http://lists.wispa.org/pipermail/wireless/ -- [email protected] ---------------------------------------------------------------------------- ---- WISPA Wants You! Join today! http://signup.wispa.org/ ---------------------------------------------------------------------------- ---- WISPA Wireless List: [email protected] Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/ -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: [email protected] Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
