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IBM Type II Twinax Cable

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jimatkci

IS-IT--Management
Jun 19, 2003
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I have a new client who said their building was wired with IBM Type II Twinax Cable... What is it, and will it work with 100 MB Ethernet? Any issues I need to worry about?
 
Twinax is not a twisted pair cable, and will certainly not work at 100MBit speed, nor will it even work as an ethernet network. It was never certified for any such purpose, and is more like a coaxial cable with two conductors.

There are devices available to convert a daisy chain based twinax system (token ring) to a star topology, however, not cheap... and would be much more efficient to rewire to current spec.
 
If it is really Type II then it may work for 100MBit ethernet. I don't think there was ever something called "IBM Type II Twinax Cable". Twinax was one technology, the "Type" cables another. Type II is a "hybrid" cable that had both the older 2+2 pair for Token Ring and 4 pair UTP for Ethernet. In my experence Type II is not as common as twinax.

Here is a listing from
Twinax
Twinaxial cable consisting of two parallel conductors surrounded by a shield. Used in the IBM 3x-AS/400 enviornment.

Type 1 IBM cable
Two 22AWG shielded twisted pairs under same jacket.

Type II IBM cable
Two 22AWG shielded twisted pairs, plus four pairs of 24 AWG UTP under same jacket.

Type 3 IBM
specification for unshielded twisted pair cable.

See also:
It all depends on exactly what you have and what you want to do with it. If you are the adventurous type and it is Type II then terminate some of the UTP portion and run a certification scanner in it, the results may surprise you. Then again it may come up as cat3 and unsuitable for 100Mbit.

For a modern standards compliant network you will need to re-cable.
 
The Standards Committee is looking at high speed data over Twinax. I will try to find the thread to get you additional info.

Regards
Peter Buitenhek
Profit Developer.com
 
5.2.4 Twinax
Twinax, or twinaxial, is a type of communication transmission cable consisting of two center conductors surrounded by an insulating spacer which in turn is surrounded by a tubular outer conductor (usually a braid, foil or both). The entire assembly is then covered with an insulating and protective outer layer. Twinax is constructed much like coaxial cable, execpt it has two center conductors instead of one. However, it is similar to twisted pair cabling in that it uses differential, or "balanced", transmission. 150-ohm twinax is specified as a "short haul" cable that can be used with the 1000Base-CX media system. Although twinax has better transmission characteristics than twisted pair media, it supports segment lengths of only 25 meters for 1000Base-CX due to the very high 1.25 Gbaud signal transmission rate.

Regards
Peter Buitenhek
Profit Developer.com
 
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