http://ps-2.kev009.com/ohland/serial/Getting_to_Know_RS-232.html

Finished reformatting the text, but there are no images yet.

Nothing earthshaking, just starting to gather period information on
serial ports. My SWAG is the Model 90 uses RS-232-D, which was released
in 1986. D added the DB25 to the standard, might have added refinements
to the signal levels.

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On 5/3/2022 13:47, Louis Ohland wrote:

http://ps-2.kev009.com/ohland/serial/Getting_to_Know_RS-232.html

Finished reformatting the text, but there are no images yet.

Nothing earthshaking, just starting to gather period information on
serial ports. My SWAG is the Model 90 uses RS-232-D, which was released
in 1986. D added the DB25 to the standard, might have added refinements
to the signal levels.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 5/3/22 12:47 PM, Louis Ohland wrote:

http://ps-2.kev009.com/ohland/serial/Getting_to_Know_RS-232.html

Having just read a 60 page book on RS-232, I'll give your page a read
for comparison.

Nothing earthshaking, just starting to gather period information on
serial ports. My SWAG is the Model 90 uses RS-232-D, which was released
in 1986. D added the DB25 to the standard, might have added refinements
to the signal levels.

Um ... so what port was the RS-232 standard using before the D revision?

Or was it purely electrical and signaling with no physical form factor specified before D? -- I'd have to go back and refer to notes / aforementioned book to answer my own question.



--
Grant. . . .
unix || die

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

From a blurry stroboscopic tour, I think -A was not specific enough for conductors. -B? -C did not have DB25, RS232 is one of those things that "everybody knows", but the actual details are not known...

I need to findt some good RS232 summaries.

From comparing the functions against the Model 90 DB25 serial port, I'd
say it does not implement the Secondary Communications Channel.

I must Czech the announcement letters for supported modems. The IBM
leased line modems might have the pinout for the DCE...

On 5/4/2022 00:11, Grant Taylor wrote:

On 5/3/22 12:47 PM, Louis Ohland wrote:

http://ps-2.kev009.com/ohland/serial/Getting_to_Know_RS-232.html

Having just read a 60 page book on RS-232, I'll give your page a read
for comparison.

Nothing earthshaking, just starting to gather period information on
serial ports. My SWAG is the Model 90 uses RS-232-D, which was
released in 1986. D added the DB25 to the standard, might have added
refinements to the signal levels.

Um ... so what port was the RS-232 standard using before the D revision?

Or was it purely electrical and signaling with no physical form factor specified before D?  --  I'd have to go back and refer to notes / aforementioned book to answer my own question.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Where are details on the IBM external modems? Like leased-line or stuff
used with consoles?

My forlorn hope was there exists a DB25 section in the manuel that
covers the pinout, maybe findting out what "Pin 12" is all about...

On 5/4/2022 06:43, Louis Ohland wrote:

From a blurry stroboscopic tour, I think -A was not specific enough for conductors. -B? -C did not have DB25, RS232 is one of those things that "everybody knows", but the actual details are not known...

I need to findt some good RS232 summaries.

From comparing the functions against the Model 90 DB25 serial port, I'd
say it does not implement the Secondary Communications Channel.

I must Czech the announcement letters for supported modems. The IBM
leased line modems might have the pinout for the DCE...

On 5/4/2022 00:11, Grant Taylor wrote:

On 5/3/22 12:47 PM, Louis Ohland wrote:

http://ps-2.kev009.com/ohland/serial/Getting_to_Know_RS-232.html

Having just read a 60 page book on RS-232, I'll give your page a read
for comparison.

Nothing earthshaking, just starting to gather period information on
serial ports. My SWAG is the Model 90 uses RS-232-D, which was
released in 1986. D added the DB25 to the standard, might have added
refinements to the signal levels.

Um ... so what port was the RS-232 standard using before the D revision?

Or was it purely electrical and signaling with no physical form factor
specified before D?  --  I'd have to go back and refer to notes /
aforementioned book to answer my own question.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 5/4/22 5:43 AM, Louis Ohland wrote:

From a blurry stroboscopic tour, I think -A was not specific enough for conductors. -B? -C did not have DB25, RS232 is one of those things that "everybody knows", but the actual details are not known...

I'm not sure about that.

The following quote comes from your page:

"In October 1963, RS-232 became RS-232-A and was modified to include a
25-pin connector with a maximum cable length of 50 feet."

So, what is different about that 25-pin connector the DB-25 that you say
was added in RS-232-D?

I need to findt some good RS232 summaries.

I'm not sure that summaries are what you want. I think you want lots of
raw data that you summarize yourself.

From comparing the functions against the Model 90 DB25 serial port, I'd
say it does not implement the Secondary Communications Channel.

I know of the secondary communications channels, but I don't think I've
ever seen them used. However, seeing as how secondary communications
channels require more than 9 pins, I think that whatever used them would
be quite old and incompatible (or down rated) with 9-pin connections.

I must Czech the announcement letters for supported modems. The IBM
leased line modems might have the pinout for the DCE...

If an old serial port is electrically compatible with a serial device
with a known pin out, you inherently have (some of) the old serial
port's pin-out. DTX must connect to DRX and control lines must be
paired in a way that functions. If you reference device is 9-pin, you obviously won't have the secondary lines. But I think you can deduce
75% or more of what you want.



--
Grant. . . .
unix || die

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 5/4/22 6:33 AM, Louis Ohland wrote:

Where are details on the IBM external modems? Like leased-line or stuff
used with consoles?

I would think that technical documentation that came out with the
original IBM PC and the likes would have the details that you are
looking for. IBM's documentation used to be quite detailed, especially
for the things that define how something external is supposed to
interface with the system.



--
Grant. . . .
unix || die

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 5/3/22 11:11 PM, Grant Taylor wrote:

Having just read a 60 page book on RS-232, I'll give your page a read
for comparison.

Some additional comments from my read of the document.

- I believe mark / space polarity is inverted between data and control
pins.

- I find that having two separate grounds; signal and frame, to be ...
odd. Pins 7 and 1 on (presumably on a 25-pin connector) are nebulous to
me. Especially when trying to use 8-pin connectors a la Yost wiring.

- You have a typo "contained in modem modems". I'm not sure if that's supposed to be "contained in most modems" or what.

- I have qualms about the description of the baud rate. My
understanding is that the baud rate is the symbol rate. Faster modems
encode multiple bits per symbol. Hence how the bit rate is higher than
the baud rate.



--
Grant. . . .
unix || die

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Added here:
https://www.ardent-tool.com/comms/Getting_Know_RS232.html

On 03.05.2022 20:47, Louis Ohland wrote:

http://ps-2.kev009.com/ohland/serial/Getting_to_Know_RS-232.html

Finished reformatting the text, but there are no images yet.

Nothing earthshaking, just starting to gather period information on
serial ports. My SWAG is the Model 90 uses RS-232-D, which was released
in 1986. D added the DB25 to the standard, might have added refinements
to the signal levels.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)