Re: T3

[Josh Karnes]

Well, to be more clear, the difference between a DS3 interface and a T3 
interface is simply that the T3 is intended to be used outside the 
building.  For example, Cisco Systems here in Austin has a T3 line which 
connects us to the backbone provider at the telephone CO, about a mile 
away.  Definitely an outside kind of thing.  DS3, on the other hand, is 
cross-connect type connection which runs only between racks in the same 
building and does not require AC power fault and lightning testing.


T3 is indeed a TNV interface.  DS3 is SELV.

Bellcore GR-1089 has tests for broadband telecommunications interface in 
section 4.6, and this would be applicable for T3.  These are pretty hairy 
tests.  There are different requirements depending on whether the equipment 
is intended to be used with an external protector, whether it's outdoor 
type equipment, etc.


T3 line protection circuit will involve a transformer, a fuse and a 
gas-tube type surge protector.  A SidACTOR type device has way too much 
capacitance to operate on a T3.  The Overvoltage and lightning tests (plus 
all other TNV type tests) in UL 1950 are applicable if the flowchart does 
not get you out of it (fire enclosure, 100A^2/sec limiting, etc.).


Good luck!

-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Josh Karnes   Lead Safety Engineer  Cisco Systems - Austin


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Re: T3

[David Gelfand]

RE: T3The line interface unit manufacturer (TDK) also says that T3 lines remain 
in the building, so it would appear that it is considered SELV rather than TNV 
therefore no power cross.  Can anyone else back this up?  Thanks to all for 
your input!

Best regards,

David.

- Original Message - 
From: Seminsky, George 
To: 'David Gelfand' ; emc-p...@ieee.org 
Sent: Thursday, February 08, 2001 10:54 AM
Subject: RE: T3


For whatever it is worth, I believe that T3 interfaces do not have to undergo 
NEBS GR-1089 Lightning and AC Power Fault testing whereas T1 interfaces do. The 
reason being that T3 interfaces are not connected to outside lines and 
therefore are not exposed to environmental nasties.

George Seminsky 
Compliance Engineering 
Nuera Communications. Inc. 
10445 Pacific Center Court 
San Diego, CA 92121 
Ph 858 625 9220 X4410 
Fx 858 625 2422 
www.nuera.com 



-Original Message- 
From: David Gelfand [mailto:gelf...@memotec.com] 
Sent: Thursday, February 08, 2001 7:27 AM 
To: emc-p...@ieee.org 
Subject: T3 




Has anyone had any experience with safety approvals to UL 1950 of T3 interfaces 
over coaxial cable - are power line cross tests required? 

Thanks in advance, 

David. 

David Gelfand 
Regulatory Approvals 
Memotec Communications Inc. 
Montreal Canada 



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