[UK-CONTEST] Keying IC-735 from computer

[Ed Taylor, G3SQX]

Hello folks,

I've just acquired an Icom 735, and I'm getting it hooked up to other bits
of hardware it might need to talk to.  The CW keying from contest loggers is
the problem -- I can't get it to work from a parallel port, either a desktop
or laptop variety (usual circuitry, as per SD or NA, etc.).  It works (sort
of) for about ten characters, then just bleeps a little in response to each
character sent.

Keying is fine for other rigs using an identical parallel interface (tried a
couple of Kenwoods).  However, the 735 works fine with serial port keying --
but I want to save the laptop's serial port for rig control.

I guess I might need something extra (couple of transistors to invert and
re-invert the keying maybe), but I wonder if anyone else has already
exercised their brain cells on this, before I plug in the soldering iron.
Any ideas, please?

73,

Ed, G3SQX