Velocity Reviews > For those Network techie geeks

For those Network techie geeks

Bok
Guest
Posts: n/a

 01-06-2004
On Wed, 07 Jan 2004 18:36:19 +1300, TEX wrote:

> System running 10base2, BNC interconnect. Computers are connected from
> the nic to the wall via a single cable. NOT a T connector. Basically you
> are extending the center of the T connector in a normal simple
> configuration.
>

Is this some kind of trick question?

You haven't specified the nature of the in-wall cabling. If the in wall cabling is 10base2 (thin net), then it
doesn't sound valid to me (but then again I'm not a network techie geek
)

> How long must the cable be from the wall to the computer???

If the in-wall cable is 10base2, then my answer to this is close to ZERO -
the center of the connector T should be connected as close to the NIC as
possible for reliable operation.

The situation will be different if there are active devices in the wall
such as a media converter (tranceiver) or repeater of some form - please
clarify.

TEX
Guest
Posts: n/a

 01-07-2004
System running 10base2, BNC interconnect. Computers are connected from
the nic to the wall via a single cable. NOT a T connector. Basically you
are extending the center of the T connector in a normal simple
configuration.

How long must the cable be from the wall to the computer???

TEX

Lennier
Guest
Posts: n/a

 01-07-2004
On Wed, 07 Jan 2004 18:36:19 +1300, TEX wrote:

> How long must the cable be from the wall to the computer???

1 x D' + 3" + H where D = the distance between the computer and the wall
and H = the distance between the floor and the plug on the wall...

;o)

Lennier

TEX
Guest
Posts: n/a

 01-07-2004
Bok wrote:

> On Wed, 07 Jan 2004 18:36:19 +1300, TEX wrote:
>
>
>>System running 10base2, BNC interconnect. Computers are connected from
>>the nic to the wall via a single cable. NOT a T connector. Basically you
>>are extending the center of the T connector in a normal simple
>>configuration.
>>

>
>
> Is this some kind of trick question?

No this is not a trick question. Just an interesting thing I discovered
today. A friend was try to explain to me the finer details...but got
lost half way through it. Thought someone might actaully know WTF I am
taking about and actually explain to me in laymans terms. I know it is
old technology now, but was an interesting learning experience.

> > You haven't specified the nature of the in-wall cabling. If the in wall cabling is 10base2 (thin net), then it

> doesn't sound valid to me (but then again I'm not a network techie geek
> )
>
>
>>How long must the cable be from the wall to the computer???

>
>
> If the in-wall cable is 10base2, then my answer to this is close to ZERO -
> the center of the connector T should be connected as close to the NIC as
> possible for reliable operation.
>
> The situation will be different if there are active devices in the wall
> such as a media converter (tranceiver) or repeater of some form - please
> clarify.

The inwall cabling is 10base2, and it utilises a "AMP" thinnet TAP
connector to interface to the NICS. Effectivly the the thinnet TAP is a
T connector, in which the center of the T is cabled to the NIC. Saves
the hassle and tangle of dual leads and T on the end of each NIC

As you have said the the center of the T has to be as close to the NIC
as possible for reliable operation, but since I have a 6ft long thinnet
tap cable, this answer is not quiet right.

TEX

Richard Malcolm-Smith
Guest
Posts: n/a

 01-07-2004
TEX wrote:

> The inwall cabling is 10base2, and it utilises a "AMP" thinnet TAP
> connector to interface to the NICS. Effectivly the the thinnet TAP is a
> T connector, in which the center of the T is cabled to the NIC. Saves
> the hassle and tangle of dual leads and T on the end of each NIC
>
> As you have said the the center of the T has to be as close to the NIC
> as possible for reliable operation, but since I have a 6ft long thinnet
> tap cable, this answer is not quiet right.

I have seen a system in some place where we were ripping it out where the wall
plate allowed for a plug to be removed and bridged the connection when it was
taken out, and the plug actually ran 2 pieces of coax up to the PC where they
terminated in a single BNC plug. Could this be what you have there?

TEX
Guest
Posts: n/a

 01-07-2004
Richard Malcolm-Smith wrote:

> TEX wrote:
>
>> The inwall cabling is 10base2, and it utilises a "AMP" thinnet TAP
>> connector to interface to the NICS. Effectivly the the thinnet TAP is
>> a T connector, in which the center of the T is cabled to the NIC.
>> Saves the hassle and tangle of dual leads and T on the end of each NIC
>>
>> As you have said the the center of the T has to be as close to the NIC
>> as possible for reliable operation, but since I have a 6ft long
>> thinnet tap cable, this answer is not quiet right.

>
>
> I have seen a system in some place where we were ripping it out where
> the wall plate allowed for a plug to be removed and bridged the
> connection when it was taken out, and the plug actually ran 2 pieces of
> coax up to the PC where they terminated in a single BNC plug. Could this
> be what you have there?
>
>

Nope. The setup was originally used for a Novell LAN, years and years
ago. Definatly a single core coax cable connected to the NIC.

TEX

Uncle StoatWarbler
Guest
Posts: n/a

 01-07-2004
On Wed, 07 Jan 2004 22:43:19 +1300, TEX wrote:

> Nope. The setup was originally used for a Novell LAN, years and years
> ago. Definatly a single core coax cable connected to the NIC.

It sounds like the old Novell 75 ohm 2Mb/s standard.

Bok
Guest
Posts: n/a

 01-07-2004

> Here's a data sheet on the AMP system:
> http://www.videkonline.co.uk/pictures/pdfs/page094.pdf
>
> The drop cables are only available in 2.5, 3.6, 4.8, 7.6m. These set
> lengths have probably something to do with the RF-side of things, but
> the theory to confirm this is beyond me.

The individual lengths of the drop cables in the AMP system are not
critical. Take a look at the description, it's not a single coax. Quoting
from the above PDF
"The drop cables are made from dual thinwire cable with an
overall PVC sheath".
This makes all the difference - each side of the coax within the drop
cable is essentially inlined on the main cable. This is not the same
as adding a single coax extension between a T adaptor and NIC where the
length would be critical (to avoid inteference from reflected signal back
on the main bus).

However, because it's dual coax, you need to allow for double the drop
length when computing the total bus length, to stay within the recommended
recommended 185meter. limit for 10base2.

To emulate this electically with single core coax you need to run two
lengths of coax from the wall to a T connector connected directly to the
NIC.

The advantage of the AMP system is that you can plug and unplug the
drop cable without disrupting the LAN because the AMP connector is make
before break, which retains continuity.

bok
Guest
Posts: n/a

 01-07-2004
> The inwall cabling is 10base2, and it utilises a "AMP" thinnet TAP
> connector to interface to the NICS. Effectivly the the thinnet TAP is a
> T connector, in which the center of the T is cabled to the NIC. Saves
> the hassle and tangle of dual leads and T on the end of each NIC

That's quite different - we had that type of cabling in one of the buildings
here at work years ago. The drop cables for thinnet taps consisted of TWO
coax cables, which loops the signal to the node, then back to the other side
of the tap. There is a microswitch in the tap assembly that allows the two
sides of the coax to be inserted creating an unbroken network which is
'electrically equivalent' to connecting with a traditional BNC T connector.

> As you have said the the center of the T has to be as close to the NIC
> as possible for reliable operation, but since I have a 6ft long thinnet
> tap cable, this answer is not quiet right.

If it's lan tap, then you are not connecting to a T connector in the wall.
Thinnet tap drop cables usually had a square looking connector into the wall
NOT a BNC connector. It's not quite right to say:

"Basically you are extending the center of the T connector in a normal
simple configuration."

This is not a valid 10base2 configuration and will be unreliable.

cheers

bok
Guest
Posts: n/a

 01-07-2004
> If it's lan tap, then you are not connecting to a T connector in the wall.
> Thinnet tap drop cables usually had a square looking connector into the

wall
> NOT a BNC connector. It's not quite right to say:
>
> "Basically you are extending the center of the T connector in a normal
> simple configuration."

Just to clarify this a bit. The tap assembly plus the drop cable are
equivalent to a T connector. It is invalid to lengthen the drop cable with a
length of coax and BNC coupler, which would be the same as inserting a
length of coax between the centre of a T adaptor and the network node (NIC).

hope this helps