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- Path: sparky!uunet!cs.utexas.edu!wupost!waikato.ac.nz!comp.vuw.ac.nz!actrix!David.Empson
- Newsgroups: comp.sys.apple2
- Subject: Re: Looking for null-modem cable source
- Message-ID: <1992Sep14.132457.29061@actrix.gen.nz>
- From: David.Empson@bbs.actrix.gen.nz
- Date: Mon, 14 Sep 1992 13:24:57 GMT
- Sender: David.Empson@actrix.gen.nz (David Empson)
- References: <1992Sep11.194829.5188@norfolk.vak12ed.edu> <BuHG9x.wB@CAM.ORG> <8rs-z=A@engin.umich.edu>
- Organization: Actrix Information Exchange
- Lines: 56
-
- In article <8rs-z=A@engin.umich.edu> dmag@engin.umich.edu (Daniel Demaggio ) writes:
- > In article <BuHG9x.wB@CAM.ORG> vandry@CAM.ORG (Phillip Vandry) writes:
- > ><1992Sep12.030234.14188@athena.mit.edu>
- > >pbauer@athena.mit.edu (Paul H Bauer) writes:
- > >>In article <1992Sep11.194829.5188@norfolk.vak12ed.edu>
- > >fculpepp@norfolk.vak12ed.edu (Fred W. Culpepper) writes:
- > >
- > >both ends. Apple created those cables specifically for the reason that if
- > >you have two DIN-8 ports, you don't have to bother with the hassle of
- > >modem cables, printer cables, null modem cables, etc.. A cable is a cable
- > >is a cable, and a cable can connect any device to any other device.
- > >vandry@champlain.cam.org
- >
- > BZZZT. Wrong. There are two types of cables: Printer cables and Modem
- > cables. The only difference is that a Printer cable has lines 2 and 3
- > switched. A printer cable will work fine as a null-modem cable for
- > connecting two computers. A modem cable will work fine as a straight-thru
- > cable (i.e. for printer switchboxes). There is a difference.
-
- If you are talking about a cable with a Mini-Din-8 connector at BOTH
- ends, then there is only one type of cable. A "Mac Plus to
- ImageWriter II" cable will also connect two Macs, two IIgses, a IIgs
- to a Mac, etc.
-
- You only get different sorts of cables where one or both ends is a
- DB-25 connector, since there are two standard DB-25 pinouts:
-
- DCE (Data Communications Equipment), e.g. modems and some computers.
- This has pin 2 for receive data and pin 3 for transmit.
-
- or
-
- DTE (Data Terminal Equipment), e.g. terminals, printers and some
- computers. This has pin 2 for transmit data and pin 3 for receive.
-
- The input/output sense of the flow control lines are opposites for a
- DTE and DCE as well. A DTE outputs on pins 4 (RTS) and 20 (DTR) and
- inputs on pins 5 (CTS), 6 (DSR) and 8 (DCD). Pins 1 (frame ground) and
- 7 (signal ground) are common to both ends.
-
-
- A 25-way straight through DB-25 to DB-25 cable will connect a DCE to a
- DTE. You need a "null modem" cable if you want to connect a DCE to a
- DCE, or a DTE to a DTE. This cable swaps signals pairs (such as Tx
- Data and Rx Data) as necessary.
-
- The Mini-Din-8 connector has the same pinout on all devices, so there
- is only one type of cable.
-
- If you have a Mini-Din-8 to DB-25 cable, there are two sorts, because
- the DB-25 may need to plug into a DCE (e.g. modem) or DTE (e.g. printer).
- --
- David Empson
-
- Internet: David.Empson@bbs.actrix.gen.nz EMPSON_D@kosmos.wcc.govt.nz
- Snail mail: P.O. Box 27-103, Wellington, New Zealand
-