Tony Peters writes:

>  I only want to send character out this port from a job every 90 seconds so
>  sensor can detect the change in voltage on one of the wires, so there is no
>  requirement for bi-directional communication.

Why not kill two birds with one stone and simply monitor the system console
instead? While you can certainly create a job to write to the console every 90
seconds or so, all of the other traffic (log-on/log-off messages written to
the system console) will only further assure your Keep Alive sensor that the
HP3000 is alive and well.

Doing this, you would only need to put a tap across data out & ground to
generate a voltage change. And added advantage of this approach, beyond being
very simple, is that it is likely to be compatible with all future versions of
the HP3000.

Wirt Atmar