Newsgroups: comp.os.vms
Subject: Re: Extension cable for DEC keyboard and mouse
From: don@zl2tnm.gen.nz (Don Stokes)
Date: 12 Dec 92 01:49:45 GMT
Distribution: world
Organization: The Wolery

leichter@lrw.com (Jerry Leichter) writes:
> Keyboards are an interesting story.  The standard cable for an LK201 (and, as
> far as I know, for subsequent keyboards - but I don't have any handy to look
> at) uses standard RJ11 (modular telephone) connectors.  (No, NOT the DEC MMJ -
> Modified Modular Jack - standard RJ11).  This means that, in theory, you can
> use a piece of telephone wire (though I don't recall if you need to find one
> that is wired "straight through" - telephone wire "swaps sides").

No, it's *not* an RJ11.  I can't remember the plug type it is, (and my parts
catalogues are positively unhelpful -- they list the part, but give only a
part number, not a "common name").  What it is is a telephone _handset_ 
cable; the connectors are four way (as opposed to six way for an RJ11).
And yes, they do swap sides.  An extension cable would have to be straight;
either that or you install a longer cable that is swapped.

I have serveral keyboard/telephone cables around here -- I tend to replace
keyboard cables with the ones from LK201s because the LK201 cables have long
stretches of straight cable whereas most keyboard cables are curly all the 
way.  My VAXstation keyboard is connected via an Amiga cable since it has
little need of the longer cable.

However, the cable that will shift the system box away from the workstation
head is a 15-way shielded cable.  The keyboard (and mouse if you're using
anything newer than the original brick) are plug into the head end of this
cable, so there's only one cable coming out of the body.  I imagine that
just adding another 15-way cable to the body end of this cable (eg a DECmate/
Rainbow/Pro/VT240 video cable) would do the trick.

My VAXstation II's head is some 8' away from the back of the machine it's
plugged into, using the standard cable.  Are more modern machines given
shorter (or even different?) cables?

> Mice, I can't help you with.  At least the old box-shaped mouse used the same
> connecter as an Ethernet AUI cable.  (I know this from sad experience:  I
> accidentally plugged a mouse into the Ethernet port of a VAXStation II.
> Killed the mouse instantly.)

You're still using that evil thing?  I keep mine around for the day I
take up fishing again.  Modern mice plug into the "digitiser" hole at the
head end of the video cable, and don't require an extra cable all the way
back to the system box.

Personally, I dislike mice that operate so badly that if you run the mouse
in a circle the pointer describes a square.  (I aquired a hockey puck mouse,
and relegated the brick to junk box where it belongs before anyone could
blink.)

> There is a potential safety problem in doing this, however.  Standard
> telephone "wire" isn't really wire - the conductors are foil.  They have

WOT?

If this is true, the US electronics industry *deserves* to go down in the 
hands of Far East manufacturers.  A quick survey of telephone and keyboard
cables around here reveals stranded copper wire in all of 'em, and I've
not seen a foil conductor in such cables yet (apart from cable shields, but
that's different).  Of course all "telephone" gear around here is of Far
East or local manufacture....

> fairly high resistance.  Older LK201's drew a fair amount of power through
> their cables.  If a short develops in an LK201, the power supply fuse is
> supposed to blow.  Apparently, if the shorted LK201 is connected through the
> foil telephone wire, instead of through the must lower resistance standard
> cable, the current it can draw remains low enough so that the fuse doesn't
> blow.  LK201's in this state have been known to catch fire.

A colleague in the dim distant past once decided he liked a third party's
keyboard but not the screen -- so he plugged the keyboard into a VT220....

He powered down Real Fast when the keyboard cable became too hot to touch...
(By some miracle, neither the keyboard or terminal were damaged.  Damn lucky.)

> At one time, DEC DID sell a keyboard extension cable.  (It was intended for
> use with a long-dead product whose name now escapes me - it was a workstation
> wannabe that used a controller that plugged into a 780 and connected to the
> tube using a fiber optic link.)  I don't know if this is still available.

The VAXstation 100.  You too could have a VAX 11/780 (or 11/750, and
presumably any other Unibus VAX) as your personal workstation.  

I thought the head connected only via the fibre.  I think I know where a
manual is for one of these....

--
Don Stokes, ZL2TNM (DS555)                        don@zl2tnm.gen.nz (home)
Network Manager, Computing Services Centre            don@vuw.ac.nz (work)
Victoria University of Wellington, New Zealand              +64-4-495-5052