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uk.comp.home-networking (UK home networking) (uk.comp.home-networking) Discussion of all aspects of computer networking in the home, regardless of the platforms, software, topologies and protocols used. Examples of topics include recommendations for hardware or suppliers (e.g. NICs and cabling), protocols, servers, and specific network software. Advertising is not allowed.

Specs for POE on 3com 7250 please ?



 
 
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  #1  
Old November 8th 08, 06:27 PM posted to uk.comp.home-networking
Quagmire
external usenet poster
 
Posts: 13
Default Specs for POE on 3com 7250 please ?

Just tried:

4+5 +ve
7+8 -ve

Fed with the points own 3v psu, via a 20M CAT5... and NOTHING !
Do 3com use a different spec ?


  #2  
Old November 9th 08, 07:18 PM posted to uk.comp.home-networking
Andrew Gabriel
external usenet poster
 
Posts: 227
Default Specs for POE on 3com 7250 please ?

In article ,
"Quagmire" writes:
Just tried:

4+5 +ve
7+8 -ve

Fed with the points own 3v psu, via a 20M CAT5... and NOTHING !
Do 3com use a different spec ?


PoE uses 48VDC (standard telephony voltage).
If you are building your own power source, make sure you include
suitable current limiting protection (1/3rd Amp, IIRC) so the cable
doesn't burst into flames in the event of a short circuit.

There are two different schemes for feeding the power down the
cable. I don't know which your item uses.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
  #3  
Old November 10th 08, 12:57 AM posted to uk.comp.home-networking
Quagmire
external usenet poster
 
Posts: 13
Default Specs for POE on 3com 7250 please ?


"Andrew Gabriel" wrote in message
...
In article ,
"Quagmire" writes:
Just tried:

4+5 +ve
7+8 -ve

Fed with the points own 3v psu, via a 20M CAT5... and NOTHING !
Do 3com use a different spec ?


PoE uses 48VDC (standard telephony voltage).
If you are building your own power source, make sure you include
suitable current limiting protection (1/3rd Amp, IIRC) so the cable
doesn't burst into flames in the event of a short circuit.

There are two different schemes for feeding the power down the
cable. I don't know which your item uses.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]




So... the original 3v PSU isn't man enough then ! that answers that....
but I have seen DIY adaptors on the net - none that I can remember mention
the higher voltage...


 




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