try null modem on serial cable (was: HP 700/92)

try null modem on serial cable (was: HP 700/92)

Post by Richard S. Shufor » Mon, 04 Jun 2001 00:30:30

to which replies are impossible, someone caused to appear as though
"Barry" had uttered:


> I've gotten my hands on an HP 700/92 dumb terminal...

>     [commendable amount of detail on software setup]

>  ...
>  my ttys file entry:
>  ...
>  my termcap file entry:
>  ...
>  output from stty -f /dev/ttyd0 -e:
>  ...
>  getty process
>  ...

>  The terminal's datacomm port is connected to my PC's first serial
>  port (com1) by means of a Male DB25 to Female DB9 RS-232C cable...
>  The terminal works in local mode, but nothing pops up in remote mode.

If this is the same type of cable that you would use to connect a
modem to a PC, then you must deal with the following situation:

(1)  The PC expects to talk to a modem at the other end of the cable.

(2)  The terminal *also* expects to talk to a modem at the other end
     of the cable.

Note that both devices want to talk to a modem.  You must do something
to satisfy this yearning.

What you need, therefore, is little item called a "null modem".

The null modem consists of a small plastic block with a female
connector on one end and a male connector on the other end, with
some tricky wiring inside.  You can buy a null modem at a Radio Shack
store, or from various vendors such as BlackBox or Digikey.  They are
available in either 25-pin or 9-pin styles.

(Pedantically speaking, the 9-pin D-shell connector is a DE-9, but
this detail is usually fudged.)

Attach the null modem to one end of the cable between the PC and the
terminal.  (For a simple asynchronous terminal, it probably doesn't
matter which end of the cable.)

Then see if the terminal can communicate better with your FreeBSD Unix


For other information on using character-cell video terminals, see:



1. HP 700/92

Sean McGranaghan's CPU sent forth this bytestream:
|       Hello, I am looking for an HP700/92 termcap or terminfo entry for
|       SCO OpenServer 5. I have tried the various built in HP types including
|       the 'hp700' entry, but they don't look right. Any suggestions are
|       appreciated.

In either case, termcap or terminfo, you're dealing with text files,
so if something doesn't look right or behave as you think it should,
you're free to make up your own new entry, modifying some prior one.


2. XFree86 2.1.1 and Cirrus Logic GD543X card

3. Linux Emulator for HP 700/92?

4. vi editor FAQ (Frequently Asked Question List), Part 1/2

5. Serial port to serial port with null modem cable

6. Installing Linux on Flash ROM (no HD) ?

7. Serial null cable modem

8. Mass Installation Tool

9. HELP: Network Connection with serial cable(NULL modem)??

10. Serial ports and Null modem cables....

11. Network with serial cable or null modem?

12. Handle a SUN Blade 10 over Serial Null Modem Cable

13. Prob: HP 300 to HP 700 conversion - library dd300l