[conspire] EIA RS-232-C, ... Re: DE-9, not DB-9 (was: ...

[Texx]

Several things:

I will admit to confusion about DE.
I always thought it was a screwup that became commonplace (Like the non
word "irregardless" that retards insist on using)


The first consumer TouchTone(tm) dials had only 10 buttons!

Trivia:
When one Central Office connects to another CO, they did NOT use the SAM
frequency pairs.
There were about 20 inter office signalling tone pairs and this is what
John Draper exploited with his "blue box"

The 16 tone pad was mostly used in military "Autovon" systems.
The ABCD that Michael mentions were actually "F" "C" "I" "P"
"Flash Override"  "Command Overide" Instantaneous Overide" and "Priority
Overide"
When you placed a call on Autovon, you used the last column of buttons to
specify the priority of your call.
Instead of getting "re order" (Fast busy) when the number of channels
through the switch were congested on an Autovon switch,
lower priority calls were simply "bumped".

I have a rare phone that has 16 buttons (Unfortunately, labelled "A B C D")
A lot of the Autovon phones, the last column with the F C I P that column
was a different button color.

Standard switch design in those days had the number of paths through the
switch to be 1/10 of the maximun number of phones that could be connected
to the switch.
A single prefix exchange "555" had 10000 possible conneections to it,
therefore there would be 1000 paths through it.
In some cases, there were more paths, but never did the number of paths
through the switch get anywhere near the macimum number of connections.

I stand by my point about the second data channel.
My info came from someone who used to design them at the time.
The second channel fell into disuse around 1970, so I doubt Michael ever
encountered one.
Actually the second channel on the DB-25 fell out of use before the Hayes
command set came into use.

The CarterPhone decision allowed consumer supplied equipment to the phone
line as long as it complied with Ma Bells standards.
Before that, you COULD connect your own equipment to the line electrically
IF you used an aproved coupler.
Arpanet was not dial up, but it DID use Bell System lines and they all had
a WECo adapter between the modem and the line.
They were often using a WECo modem too.

I dont have the numbers hands, but indeed the second data channel HAD a
slower baudrate than the primary channel.

For the primary channel you had T R RTS CTS DSR DTR CD Data Ground.
For the secondary channel, you had the same,

  1 Protective ground
  2 TX data 1
  3 RX data 1
  4 RTS 1
  5 CTS 1
  6 DSR
  7 Data ground 1
  8 CD 1
  9 Test
10 Test
11 Spare
12 CD 2
13 CTS 2
14 TX data 2
15 TX clock DCE
16 RX data 2
17 RX clock
18 Spare
19 RTS 2
20 DTR
21 Sig quality
22 Ring indicate
23 Signal rate detector
24 TX clock DTE
25 Spare

Both channels share the DSR & DTR and both grounds.
The grounds were usually separate.
Notice the clocks?
In the early days, there were a lot of syncronous data connections, no
longer needed.

Before ethernet became widespread, a lot of places including DUAL Systems
corp ran 600k synchronous "Berk Net"
I know this because I used to support it and I had a whole workbench of
modems & RS 232 stuff.

With these connecttors, the gender is confusing.
The one with the pins is actually the female because the body of the one
with the sockets fits inside.
A lot of companies preferred to buil;d their hardware with the male DB on
the back because this kept the pins on the cable
and cables were easier to replace than pull apart the chassis and connect a
new one.

In the 80s, the industry realized that Most of the pins were no longer used.
As a result of the disuse of those pins was that they could move to a
smaller connector.

I remember that oddball serial port sun used.
It was basically a way to avoid installing a second serial port on the
chassis itself by hanging the other serial port off the secondary channel
and THAT ONE DID have equal speed between the 2 channels.
There was a problem with it though.
If you had a laptop connected to it and you rebooted the laptop, it would
do something oddball to the handshake pins and cause the server to halt.

I stand by the point that USB is TTL, well almost.  It still has come
through the USB controller chip on the server.

RS232 is polar, with plus and minutes and zero to 3v of either polarity
being invalid.
Many serial interfaces now accept either standard RS232 OR  0 and 5v
Some of those USB to serial have an embedded chip inside the plug and some
just shoot the TTL from the USB controller chip.
Actually the USB data is using the new 3.3v ttl rather than the
conventional 5v ttl.

Modern genuine RS232 are usually +5 & -5 while originally it was usually +
& - 20.

I still have a current loop teyetype.

While Michael hasnt seen some of these things, his experience has been with
newer hardware.
I have a habit of playing with "Bear skins & stone knives".

Why does this matter?
Well disagreeing with John "Giovanni" Reagan,  you cant know where you are
going if you dont know where you have already been.
The orther reason is that history repeats itself.
Technology comes back repackaged multiple times (Containers, virtual
machines, etc)

-- 

R "Texx" Woodworth
Sysadmin, E-Postmaster, IT Molewhacker
"Face down, 9 edge 1st, roadkill on the information superdata highway..."
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