NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/comp/dcom/telecom/12108

Internet Message Format | 1992-11-21 | 5.7 KB

Path: sparky!uunet!zaphod.mps.ohio-state.edu!news.acns.nwu.edu!telecom-request
Date: Sun, 22 Nov 92 00:45:02 GMT
From: [e-mail] (Todd Inch)
Newsgroups: comp.dcom.telecom
Subject: Re: Help With Keyline System
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In article <[e-mail]> infmx![e-mail]
(Jack Stephens) writes:

> I'm about to move into a house that is currently outfitted with an
> older phone system ("key line", I think). It uses older phones and
> five lighted push buttons connecting to some sort of central trunk.

In phone system lingo, "key" means "button" or "switch", so a key
telephone system has buttons to select features and lines.  A "line
key" would be a button to select a particular line.

If yours has the "a little longer than single line" phones with the
huge 1/2" diameter cables and the 25 pair (50 conductor) connectors,
it's probably a 1A2 system, which was very popular and reliable.
These usually have a Key Service Unit (KSU) under a big beige housing
bolted to the wall with a grey power supply and lots of model 66
connection "punchblocks" nearby.

I have done a little work on these and installed one in my home.

Some "gotchas" are: How/where to find the cable and 25 pair
connectors.  I usually scrounge these.

In one case, I was able to remove the 25 pair cable from an office
where they had modular adapters plugged in their ends and replace them
with cheaper three-pair cable and proper modular jacks which I
purchased.  I calculated that if I had to buy all the cable and
connectors to wire my house, I could have bought a small PBX phone
system for the price and used cheaper wire and jacks!

Whenever possible, leave the connectors attached to the cable ends.
The older connectors solder on, which you can do with a solder iron,
but it's a lot of work.  The newer ones use insulation displacement/
piercing connections which are supposed to use a special tool but can
be done manually with pliers/screwdriver if necessary, but you have to
be very careful and it also takes time.

Another gotcha: The 66 punch blocks, usually white with 25 rows of
little metal clip/fingers.  If there are five columns, all five of
each row are internally interconnected.  If there are four columns,
the left two are probably separate from the right two- - wiggle them
and see if the entire row wiggles.

DO NOT spread apart the metal fingers to insert wire or shove anything
into the clip cracks other than the wire.  You should really buy the
special tool for this -- the cheap ones are about $25.

If necessary, you can shove the wires in by straddling the clip with
needle-nose pliers.  Don't strip them first, the clip will rub the
insulation out of the way and make contact with the conductor.  I'd
highly recommend powering down the system when making connections
unless you have the proper punch tool -- it's too easy to short the
rows of clips together.  A sharp wood chisel (that you aren't
particularly fond of) can be used to trim the wire beside the clip
after shoving it in.

If you are adding an extension, you can just split off an existing
jack, except if you have individual intercom numbers to buzz/ring
individual phones you will either have both phones on the same
extension, have to disconnect the bell or buzzer in one phone, or have
to wire the bell/buzzer of phone phone onto a non-standard unused pair
and connect it to an unused intercom ring pair back at the KSU.

I REALLY prefer to run a separate "home run" to each jack directly
from the punch-blocks because it makes wiring so much easier than
trying to splice and increases flexibility.  Example: I'm running
serial RS232 over some unused pairs of some jacks, but use those same
unused pairs for the VCR remote control at other jacks, and run audio
between speakers and the amplifier at other jacks.

Also, if you try to run too many phones off one cable the lights keep
getting dimmer as you add phones and the brightness depends on how
many lights are lit, etc.  It's asthetically unpleasant if one line on
hold flashing on-off causes another line in-use to flash dim-bright.
It looks like there's a photon shortage or something.

If you have to, you can run some 50, 100 or 200 pair wire into a
closet halfway between the jack and KSU and install more punchblocks
there (if, say, you can get a bunch of cables with ends but they
aren't quite long enough.)  In fact, I'll give you some of this cable
(got a nice hunk of 400 pair about 100 feet long out of a dumpster) if
you want to pay shipping -- I keep tripping over it in the garage.

Remember -- the bells (or ringing phone lines) are operated by about
100 volt dc pulses which will wake you up (on the wrong side of the
bed) if you aren't paying attention.  And, these voltages are present
on those uncovered 66 block and the connectors -- don't let small
children (or coerce your delinquent teenagers to) put their fingers in
them.

The following accessories might come in handy.  They are available from
places like Graybar, or maybe try a local small business phone
installer:

- Two-way splitters for 25-pair connectors.
- Extension cables with male and female connectors on opposite ends.
- 66 punch blocks with connectors built into their sides.
- Phone jacks (25 pair connectors) inside little boxes that mount on
the wall and have the 66-type clips inside for connection to the cut end
of a cable.

Send me e-mail if you have specific questions or need names/numbers of
suppliers of used phones/equipment.  You can even buy used 66 blocks.

Now you know why the phone company will charge you so much.  :-)