[u3b.tech] modular null modem pinout?

rk@bigbroth.UUCP (rohan kelley) (05/15/89)

I'm trying to make a direct connect between a bell tech 386/25 and
a 3b2/400.  The port on the 386 is an ace intelligent port board
with 8 modular ports and on the 3b2 an enhanced port board.

I'm trying to construct a modular null modem cable.  This is the
wiring diagram I've come up with, but haven't tried it yet.  Does
anybody know if this is correct?

386/ace board                          3b2/enhanced ports board

1  G   <-----------------------------------------> G

2  CTS <------|                      |-----------> CTS
              |                      |
3  TDXO<......|........\/------------|-----------> TDXO
              |        /\            |
4  DTR <------|------\/  \/..........|...........> DTR
              |      /\  /\          |
5  RXDO<------|-----/  \/  \.........|............> RXDO
              |        /\            |
6  DCD <......|......./  \-----------|------------> DCD
              |                      |
7  G   <------|----------------------|------------> G
              |                      |
8  RTS <------|                      |------------> RTS


What I'm trying to say is:

G       1    to   1  G
CTS     2 tie to  8 (plug)
TDXO    3    to   5  RXDO
DTR     4    to   6  DCD
RXDO    5    to   3  TDXO
DCD     6    to   4  DTR
G       7    to   7  G
RTS     8 tie to  2  (plug)

Neither the 386 or 3b2 have DSR (RS232 pin 6) which is usually tied to
DTR.  Is it needed?
=======================================================================
Rohan Kelley -- UNIleX Systems, Inc. (Systems and software for lawyers)
UUCP:  ...{gatech!uflorida,ucf-cs}!novavax!bigbroth!rk (office)
                                   novavax!mdlbrotr!rk (home)
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3365 Galt Ocean Drive, Ft. Lauderdale, FL 33308 Phone: (305) 563-1504

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