John Zoltak writes:

> Monitoring for a voltage change on data-out would not work if someone
>  moves the console.

The console messages aren't a necessary condition of the Keep Alive circuit,
merely icing on the cake. A small job sending a message to Port 20's session
every 90 seconds would be all that's necessary, regardless of whether or not
it was the console at the moment.

I would suggest the message be "Esc A CR LF". This message would cause the
cursor on the terminal to simply recycle in place.

What would kill the circuit would be if someone should sign on to another
session on the Port 20/console terminal. The Keep Alive job would have to be
restarted with the new session number entered. Alternatively, with 10 minutes
more programming, the program could be made to seek out and find the session
number of the Port 20 device automatically. The only killer would then be that
someone would simply sign the terminal off by doing a ":BYE". But I would
suspect you'd find that out in about two minutes :-).

Wirt Atmar