Serial Cable Conventions
-------------------------


::

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 With DB25 connectors, usually (?):
    DCE is female (modem)
    DTE is male (PC com port)
 
 DB9 on PC and AT: male
 
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 RS-232 definitions:
                             DB-25       DB-9
                           DTE   DCE   DTE   DCE
 Protective Ground    PG     1     1
 Transmit Data        TD     2     3     3
 Receive Data         RD     3     2     2
 Request To Send      RTS    4     5     7
 Clear To Send        CTS    5     4     8
 Data Set Ready       DSR    6    20     6
 Signal Ground        SG     7     7     5
 Carrier Detect       CD     8     8     1
 Data Terminal Ready  DTR   20     6     4
 
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 PC             Com1:      Com2:
    IO ports   3F8-3FF   2F8-2FF
    IRQ            4         3
 
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 BB Electronics 232-422 converters:
    model 422COR has a female DB25 on the 232 side, to plug
    directly into the male DB25 DTE port of a PC:  That is,
    it is wired as a DCE, like a modem.
                PG       1
                TD       3
                RD       2
                RTS      5 _
                CTS      4 _|
                DSR     20 ___
                SG       7    |
                CD       8 ___|
                DTR      6 ___|
 
    On the RS422 side, the male DB25 has:
                TDA(-)   2
                TDB(+)   14
                RDA(-)   5
                RDB(+)   17
                gnd       7
                12V +    25
                12V gnd  12
          signs indicate polarity with no data.
 

 =====================================================

WH300 power/communication cable 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


.. -------------------------------------------------------
.. |7pin_impulse_db9| image:: 7pin_impulse_db9.png
            :alt: pinouts for WH300 power/communication cable
..   _7pin_impulse_db9: 7pin_impulse_db9.png
.. -------------------------------------------------------


|7pin_impulse_db9|_