Subject: Re: VS3100 serial cable
To: Michael Sokolov <sokolov@alpha.CES.CWRU.EDU>
From: Tim Shoppa <firstname.lastname@example.org>
Date: 02/22/1998 08:07:40
> > [...] or you can pay me to make a cable assembly for you.
> How much do you charge?
If you're local, lunch at McDonald's is good enough. I've never actually
sold one for cash - I've just made them as favors for folks I was trading
other items with.
> Do you only make MMJ-to-MMJ cables, or do you
> also make MMJ-to-DB25?
I can make a number of cables:
1. MMJ to MMJ. Used for connecting later DEC terminals and printers
to VS3100's and other computers/terminal servers with MMJ cab kits.
This cable *always* has a "twist" in it mapping 1<->6, 2<->5, 3<->4.
That's the wonderful thing about the DEC MMJ scheme: there's no
worrying about DTE vs DCE!
2. MMJ to standard RJ11, with the RJ11 using the same MMJ pinout.
Or RJ11 to RJ11. In either case, the cable again has a twist.
I then plug the RJ11 into one of the adapters below.
3. RJ11 to DB25M and RJ11 to DB25F adapters. Generally the
DB25M's are wired as DTE's (to plug into a piece of DCE,
such as a Modem, for example),
while the DB25F's are wired as DCE's (to plug into a DTE,
such as a computer or a terminal.) I can also make RJ11
to DB25F's and RJ11 to DB25M's with a "null modem" built
into the RJ to DB adaptor, to handle the cases of oddball
equipment that have the "wrong" DB sex on them.
There's several hundred feet of serial wiring in my house, all
made with the above components. They all use the MMJ pinout for
the modular cable, whether the plug is MMJ or RJ11. I dinked
around with other pinouts before standardizing on MMJ; it is
just *the* obvious choice as I can take the end of a cable and
plug it into an adapter anywhere and it simply works - no worrying
about DCE vs DTE after I've bolted the RJ<->DB adapter onto the equipment!
If I had to set some prices, I'd say US$5 for any modular cable with
any ends, as long as the cable is less than 15 feet long. Add US$10
for a RJ<->DB25 adapters at one end, wired up nicely with the inner
two conductors both going to pin 7 (ground) of the DB25. (Just like
the DEC adapters.) Tack on US$3 shipping for USPS priority mail
delivery of the resulting cable.
> Do you use proper MMJ plugs or shaved ones?
Proper MMJ plugs, of course. They're far from expensive or hard to find!
> Can you
> make a cable that looks _PROFESSIONAL_, i.e., no worse than a genuine DEC
> one? That means no uninsulated conductors sticking out, etc.
Absolutely. The trick to making a good cable is to use a proper
crimping tool that also does the strain-relief correctly. Cheap
crimpers (i.e. the plastic $5 tools at Wal-Mart) don't do this