Listers:

We're trying to save some money (so what else is new?) and not have to
spend $90 each for HP's 40233A modem cables (we need 32 of them) to
connect a rack of modems to some DTC ports (DTC16 with MDP {Modem
Distribution Panel} expansion ports). So we made some cables wired like
the 40233A cable, and we're trying to make them work.

We have *one* HP 40233A cable, which works: we can connect via modem to
the DTC and get a system prompt. But when we use the same modem and the
same DTC port with the cables we built, the modem answers and then
immediately disconnects.

Strangely, the OpenView DTC MGR reports that the MDP ports are good, i.e.
Board Status shows the ports as green. When we used the wrong cable,
92219Q, the ports showed up red. If we reverse the ends of the cable and
plug the Modem end into the DTC port (like we accidentally did on one
cable, oops), it also shows up red. So I don't think it's the DTC that's
disconnecting us, but I could be wrong.

Here are the cable specs from HP's DTC Racking & Cabling Guide (mfg # 5961-6410,
order # 5961-0373), page 58:
                 *  *  *  *  *  *
RS-232 Connection to modems
This cabling scheme is recommended for connecting modems to a DTC.
Existing HP cable: HP 40233A

25-pin male connector             25-pin male connector
       to DTC                            to modem
---------------------             ---------------------
 1 - PGND    -         ---------   1 - PGND    -
 2 - RD      INPUT     <--------   3 - RD      OUTPUT
 3 - TD      OUTPUT    -------->   2 - TD      INPUT
 4 - DCD     INPUT     <--------   8 - DCD     OUTPUT
 5 - GPO     OUTPUT
 6 - DTR     OUTPUT    -------->  20 - DTR     INPUT
 7 - SGND    -         ---------   7 - SGND    -
 8 - RTS     OUTPUT    -------->   4 - RTS     INPUT
 9 - RI      INPUT                22 - RI      OUTPUT
20 - DSR     INPUT     <--------   6 - DSR     OUTPUT
22 - CTS     INPUT     <--------   5 - CTS     OUTPUT

Note: the DTC does not monitor the RI signal from the modem.
                 *  *  *  *  *  *
You will notice that, while several pairs cross (2-3, 4-8, 6-20), others
go straight through (1-1, 7-7) and still others have pins with no
corresponding match at the other end. This is the way the cable is
supposed to be, according to HP.

So why doesn't it work??? The only difference that is readily apparent is
that the connectors on the cables we built have all 25 pins, even though
they aren't wired, whereas the HP cable only has the pins it actually
uses. But that wouldn't cause this behavior, would it? Or could it?

Getting desperate,
Patrick
--
Patrick Santucci
Technical Services Analyst
Seabury & Smith, Inc.