The following image shows a contraption I put together from my collection of tools of the trade when RS-232 serial cables and VT-100 terminals and emulators ruled the world. Anyone remember the Kermit protocol or Compuserve bulletin board service? I call this the RS-232 Mobius Strip:

RS-232 Mobius Strip

RS-232 Mobius Strip

Here is the key to interpretation (Rube Goldberg would be proud):

  • A: RS-232 Serial Cable with female DB-9 on right and male DB-9 on left.
  • B: DB-9 male-to-female Gender Mender.
  • C: Male DB-9 to female DB-25 Port Adapter.
  • D: DB-25 Serial Cable with male DB-25 on both ends.
  • E: DIGITAL brand DB-25 DEC-Connect Adapter.
  • F: DEC-Connect Serial Cable. (Like a Cat-5 Ethernet cable but with asymmetric latch clips and ribbon cable layout instead of twisted pair.
  • G: Another DEC-Connect Adapter.
  • H: Male DB-25 to male DB-9 Port Adapter.
  • I: Another DB-9 male-to-female Gender Mender.
  • J: Male DB-9 to female DB-25 Port Adapter.
  • K: DB-25 female-to-male Gender Mender.
  • L: Female DB-25 to male DB-9 Port Adapter.
  • M: DB-9 Null Modem. This puts the twist into the loop to produce the Mobius Effect. Electrons flowing thru the loop alternate between the terminal and host signal pairs on each pass.
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