Source for MMJ cables.

Johnny Billquist bqt at
Wed Dec 10 12:23:25 CST 2008

tiggerlasv at wrote:

> I don't have a source for MMJ cables,
> but I do have a US/Domestic source for MMP's
> (the offset modular connectors). . .
> They are .14 / each for flat cable, and .41 / each for round cable.
> Last I checked, they don't ship internationally.
> There are two different styles of DecConnect cables;
> both inverted, and not inverted.?? The only difference
> of course, is that one connector is flipped on one end.

Correct. And excellent info.

> When used with genuine DEC adapters, one?style worked
> for printers (DCE), and the other style worked with terminals (DTE).

Um. No. :-)
Both printers, terminals and computers are DTE.
DTE means data terminal (or terminating) equipment, while DCE means data 
communcation equipment. A typical DCE is a modem.

DEC was one of the few companies that actually got this right, and made 
cables and connectors that actually followed the standard (well, until 
the switched to MMJ anyway, which was a standard of it's own).

If just every computer manufacturer had read the specs, the world would 
have been much nicer, but what can one expect from companies who just 
didn't put in the effort because of money and lockins (most anyone), or 
just was too big to even bother (IBM).

The other company I know of who was pretty good at actually following 
the RS-232 standard is HP.

> Back in the early 90's, our office used uVax 2000's,
> connected to VT220's. along with various printers,
> connected using DEC MMJ <> DB25 adapters.
> You couldn't simply swap the DecConnect cables
> because of the inverted MMP's on some of the cables.
> All of our cabling and adapters were unmodified DEC products.

Well, which adapter worked was obviously based on which cable you had. :-)
You still got four combinations, two of which would make you happy.


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