[comp.dcom.lans] Telco-style push down blocks and stranded cable

roy@phri.UUCP (Roy Smith) (01/06/87)

	Having finally gotten fed up with the spaghetti in our machine
room, I've decided to redo all the terminal wiring using telco-style
pushdown blocks.  For historical reasons, we've got about 100 lines coming
into the machine room for 40 ports -- some are lines run to offices in
anticipation of future needs, some are lines no longer in use but which
might be needed again some day.

	What I want to do is set up a panel with a termination for each
port on one side and a termination for each external line on the other and
patch between them as necessary.  Since patching won't be frequent, I don't
need anything as fancy as plug-in patch panels; re-doing a punchdown jumper
will be easy enough.  The problem is that we've got miles of Belden 8723
(stranded shielded twisted pair) all through the building and I understand
that punchdown blocks are made to only work with solid wire.  Has anybody
tried using stranded wire in punch-down blocks?  Will it work?  The last
thing I want is to have hundreds of connections start to work themselves
loose in a year or two.

	We wire our runs like this:

          1 ----------------------------------- N/C
 Computer 2 ----------------------------------- 3     Terminal
   End    3 ----------------------------------- 2       End
          7 =================================== 7

	The frame ground is connected to the shield only at the computer
end and xmit and rcv are each twisted with a signal ground (we run 9600
over 250+ feet, and one 19.2k line over about 100 feet with no problems, so
I must be doing something right).  If the 20-30 feet between the patch
panel and the computer is 8723, as is the external line, will I loose much
if I make the patch between them plain unshielded solid phone wire?  Do
impedance mismatches make any difference at these rates, or should I just
be worried about how many feet of wire are exposed to EMI, or are the noise
margins good enough that I shouldn't even worry about that?  I suppose it's
obvious, but I guess I should mention that we're talking RS-232.
-- 
Roy Smith, {allegra,cmcl2,philabs}!phri!roy
System Administrator, Public Health Research Institute
455 First Avenue, New York, NY 10016

"you can't spell deoxyribonucleic without unix!"

holtzman@mit-amt.MEDIA.MIT.EDU (Henry N. Holtzman) (01/07/87)

Do not use standard punch down blocks and stranded wire.

Let me repeat, do not use standard punch down blocks and stranded wire.

Even if you get a good connection, you will probably sever all but one
or two strands of the wire.  Next time you work on the block you may
pull on the cable and break the remaining strands.

In fact, you should not use standard punch down blocks with anything
but wire which is meant to go in them.  If you use the wrong gauge or
the wrong softness wire then you can either ruin the block, or get a
bad (immediately, or time decaying) connection.

Now for the brighter side:

	There are companies that make stranded wire punch down blocks.
One of them is Gentner, another is ADC.  Contact a broadcast audio
supply store for more specific information.  Call the business number
of one of your local radio stations and ask for the Chief Engineer if
you can't find anybody in the yellow pages.  S/he will undoubtably
have a made purchases somewhere.

-Henry

Disclaimer:  I don't make or sell punch down blocks; I just use 'em.

silber@batcomputer.tn.cornell.edu (Jeffrey Silber) (01/07/87)

We use Belden stranded cable (8243?  I am at home, so I am not sure), but it is
22 ga stranded.  We punch those down all of the time.  By the way, if you are
buying a punch down tool GET A GOOD ONE!  We bought a cheap one from Black Box
(where we buy our blocks) and it really was unpleasant.  I finally coughed up
the $80 or so to buy the spring loaded version from Jensen Tools and my tech
will now speak to me again!

-- 
A million here, a million there ... they all add up.
********************************************************************************
Jeffrey A. Silber/silber@tcgould.tn.cornell.edu
Business Manager/Cornell Center for Theory & Simulation in Science & Engineering

grr@cbmvax.cbm.UUCP (George Robbins) (01/07/87)

In article <2551@phri.UUCP> roy@phri.UUCP (Roy Smith) writes:
>
>	Having finally gotten fed up with the spaghetti in our machine
>room, I've decided to redo all the terminal wiring using telco-style
>pushdown blocks.  For historical reasons, we've got about 100 lines coming
>into the machine room for 40 ports -- some are lines run to offices in
>anticipation of future needs, some are lines no longer in use but which
>might be needed again some day.
>
Bad idea - it will work, but reliablility suffers greatly.

The idea is if you stuff wire with insulation into a limited gap, the
insulation will be displaced and the wire will make a good connection.

If the wire is to wrong size, or compressible, or the insulation
doesn't behave properly, you'll have nothing but problems in the
long run...
-- 
George Robbins - now working for,	uucp: {ihnp4|seismo|rutgers}!cbmvax!grr
but no way officially representing	arpa: cbmvax!grr@seismo.css.GOV
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)

rab@well.UUCP (Bob Bickford) (01/07/87)

In a previous article Roy Smith asks:
> 
> 	What I want to do is set up a panel with a termination for each
> port on one side and a termination for each external line on the other and
> patch between them as necessary.  Since patching won't be frequent, I don't
> need anything as fancy as plug-in patch panels; re-doing a punchdown jumper
> will be easy enough.  The problem is that we've got miles of Belden 8723
> (stranded shielded twisted pair) all through the building and I understand
> that punchdown blocks are made to only work with solid wire.  Has anybody
> tried using stranded wire in punch-down blocks?  Will it work?  The last
> thing I want is to have hundreds of connections start to work themselves
> loose in a year or two.
> 
  Nope, it won't work.  I've done this; it will come back and haunt you
(or your successor <grin>) if you try it.  The whole mechanical design
of the silly things (telco punch-down blocks) is centered around a
single solid strand of the right size.  If you stick to that, they're
wonderful, though.

  On your wiring, the way you've set that up should give you wonderful
performance.  I was running between two and three hundred feet at 9600
baud on just plain old telco wire (doubled the signal ground) and it
worked fine....  In fact, I believe the entire building was wired that
way.
  Using the shield is both good and bad..... good if you have or
suspect EMI problems, bad on long runs because of the extra
capacitance.  Don't have my Belden catalog handy, but I seem to
recall that the stuff you mention is low-cap, so you should be ok.

-- 
Robert Bickford    {hplabs, ucbvax, lll-lcc, ptsfa, msudoc}!well!rab
terrorist cryptography DES drugs cipher secret decode NSA CIA NRO IRS
coke crack pot LSD russian missile atom nuclear assassinate libyan RSA
 The above is food for the NSA line eater.  Add it to your .signature and
 you too can help overflow the NSA's ability to scan all traffic going in or
 out of the USA looking for "significant" words.  (This is not a joke, sadly.)

paul@osu-eddie.UUCP (01/08/87)

At Ohio State, we have been using punchdown blocks for quite a while.  They
seem to work just fine, but we use only single conductor (3 conductor
telephone wire) to wire and cross connect.  You might try striping about
1/4 inch and tinning it, then punching in the tinned part. (or, how to make
stranded into single conductor wire).

		-- Paul Placeway
		   Ohio State CIS dept.
		   paul@ohio-state.ARPA
		   cbosgd!osu-eddie!paul

zemon@felix.UUCP (Art Zemon) (01/09/87)

I have a couple of hundred terminal wires running through
telephone punch down blocks and am very happy with the
arrangement.  The stranded wire works fine and the punch
down block cuts the insulation of the thicker wire just
fine.

You can also buy blocks with a 50 pin connector prewired on
them.  Then you buy cables which split from a 50 pin
connector into six DB25 connectors.  Add an extension cord
of the right length and you don't have to do any
complicated wiring between the computer and the punch down
blocks.

I've gotten my stuff from LANplex and am extemely happy
with both the products and the services.  They have some
offices on the East coast.  The number of the local office
is (714)680-8686.  They should be able to get you in touch
with someone closer to you.

Good luck,
-- 
	-- Art Zemon
	   FileNet Corporation
	   Costa Mesa, California
	   ...! {decvax, ihnp4, ucbvax} !trwrb!felix!zemon

zemon@felix.UUCP (Art Zemon) (01/09/87)

In article <600@mit-amt.MEDIA.MIT.EDU> holtzman@media-lab.MEDIA.MIT.EDU (Henry N. Holtzman) writes:
>Do not use standard punch down blocks and stranded wire.
>
>Let me repeat, do not use standard punch down blocks and stranded wire.
>
>Even if you get a good connection, you will probably sever all but one
>or two strands of the wire.  Next time you work on the block you may
>pull on the cable and break the remaining strands.
>
>In fact, you should not use standard punch down blocks with anything
>but wire which is meant to go in them.  If you use the wrong gauge or
>the wrong softness wire then you can either ruin the block, or get a
>bad (immediately, or time decaying) connection.

I disagree with all of that.  I'm using standard telco
style punch down blocks and have had nothing but good
experiences.  The blocks show no appreciable signs of wear
(and even if they do die early, they only cost about $13).
I have used a number of different brands of standed cable,
all about 22 or 24 gauge.  Removing the cables is tough;
the blocks hold on very tight and the cables are not broken
by the "teeth."  I have examined a number of cables after
removal and the strands are not broken.

Feel free to write or call if you have more questions.  My
phone number is (714)966-2344.
-- 
	-- Art Zemon
	   FileNet Corporation
	   Costa Mesa, California
	   ...! {decvax, ihnp4, ucbvax} !trwrb!felix!zemon

pozar@hoptoad.uucp (Tim Pozar) (01/09/87)

In article <2856@osu-eddie.UUCP> paul@osu-eddie.UUCP (Paul Placeway) writes:
>
>At Ohio State, we have been using punchdown blocks for quite a while.  They
>seem to work just fine, but we use only single conductor (3 conductor
>telephone wire) to wire and cross connect.  You might try striping about
>1/4 inch and tinning it, then punching in the tinned part. (or, how to make
>stranded into single conductor wire).
>

    I missed the previous postings.  I assume your discussing the merits
of punch/crunch/66 blocks.  We're using the blocks for high density, quick
changing connections for audio at our station.  I'm using Belden 8451 wire
with the blocks.  8451 is a 22ga., foil shield with drain wire, single
pair, stranded cable.  We punch it down with the insulation intact with a
standard punch tool.  Stripping the wire first, because of the density of
the connections, is not a good idea.  The exposed wire is too vunerable to
shorts with frayed wires and the wire laying across other connections.
Before we decided to use stranded wire we tested punch connections with
8451, 8450 (solid), and several other brands of simular wire, one being
Naglix.  I also have been using 8451 with these blocks for the past 6
years.  During this years I haven't had one connection that I have had to
repunch due to oxidation  or bad punches.
   . Before we punch down the connections, we paint the blocks with a
non-oxidizer from Caig Labritories.  Just for my peace of mine...
     I would like to add that we also research differant type of
connection blocks.  We also have results originated by the military
comparing different type of connections vs. life expectancy.  If anyone is
interested in this data, you can send me mail and we can make arrangements
for sending it to you.

pozar@hoptoad.uucp (Tim Pozar) (01/09/87)

   The address is --
       Tim Pozar
       KLOK-FM
       77 Maiden Lane
       San Francisco, CA 94108
       (415) 788-2022 x330

brian@sdcsvax.UCSD.EDU (Brian Kantor) (01/10/87)

Here at UCSD we have been using punchblocks (66-type) for some time.

The system we devised for using them is that each computer port is
connected to modular plugs (we use the ones from MOD-TAP), and a
"hydra" which takes the individual modular plugs and brings them to
telco-style 50-pin plug inside the computer system (Unibus cabinet,
etc).  A 25-pair cable with appropriate connectors takes this to a
dual-connectorized 66 block on the wall.  For ports which connect to
our LAN or which run to rooms with clusters of terminals, a similar
cable leaves the other half of the 66-block and runs either to a hydra
and modular plugs into the LAN box, or to another punchblock (single
connectorized is ok here) and punched-down inside wire to terminals, or
to a "harmonica" (the other sex of a hydra: modular jacks on a 50-pin
connector).  This way my cross-connect wiring for the majority of our
connections (in the computer room, at least) consists of bridging clips
and is very fast to connect.

Essentially, all RS-232 connections entering the computer room
terminate on a punchblock.  In laboratories and terminal rooms where
I'm likely to have a cluster of connections (i.e., more than 2), I
place a 66-block with 50-pin connector and run a 25-pair cable with
connectors back to the computer room, where it terminates in another
66-block.  Cross-connect is done by bridging clips or 3-pair inside
wire.  For less-dense terminals, either a punchblock is nearby serving
several rooms, or I string longer runs of 3-pair.  I've got 200 and
300 foot runs running at 19,200 and 9600 bps with no problems.

I've also bought a couple of items for troubleshooting - I have a nifty
little connector that you can slip onto the punchblock terminals and
plug a modular connector into - that connects to a breakout box or
datacomm analyzer and you can tap into any line in or out of the
computer without unplugging anything.  If you need to isolate a
connection, you can pop the bridging clips, or simply unplug the
modular plug at the terminal or computer.  Fast fast FAST to
troubleshoot!

Standardization:  We chose a 6-conductor scheme (which gives 8 ports 
on a punchblock, cable, hydra, or harmonica) so that we could wire
modems, printers, and terminals the same way.  (Our LAN boxes look like 
modems and need DTR and CD in addition to the normal TD, RD, and SG, so
we have one spare wire left over.  On modems, that spare wire is RI.)

We use only two kinds of connectors (called a 260 and a 523 by Mod-Tap)
and stock them in both sexes.  A cable with a 260 connector on both
ends is a straight-through cable suitable for connecting to a modem or
LAN box on one end, and a computer or terminal on the other (assuming
the computer is DTE, which most are these days).  A directly-wired
terminal (or other DTE device, such as a printer) will still have a 260
connector on it, but the port on the computer will have a 523 connector
for that line, which gives a null modem to connect the DTE to the
computer DTE port.

Our modem telephone lines are wired similarly, but we use 4-conductor
cable there to match the 2-pair inside wiring that the phone company
uses.  (By the way, ThePhoneCo is happy to terminate incoming lines on
one of our connectorized 66 blocks.  We just tell them to "terminate on
customer-provided RJ21X" and they do it just right.)  With 4-conductor
modular stuff, you get 12 per cable/block/hydra/harmonica.

All this stuff is available from MOD-TAP.  We buy a lot of it from
other people too. What with the installation of our LAN and rewiring
most of the campus, we've probably installed more than 2000 RS-232
connections using variations of this system, and found it to work quite
well.

DEC and others have similar systems with slightly different standards.

	Brian Kantor	UCSD Office of Academic Computing
			Academic Network Operations Group  
			UCSD B-028, La Jolla, CA 92093 USA

Disclaimer: just because I said it doesn't mean its right.  Think for
yourself.